I'm not saying we shouldn't. I'm merely asking how (on the premise that the promise is literal, earthly and irrevocable) you reckon the (earthly) throne of David to have been continually occupied since David was around.
The point was never that it would be simply continually occupied, but that there would come a day wherein it would be continually occupied righteously: a day when Israel would no longer be in apostasy, and under one apostate king or another; during such apostate times...
A time would come under a King who's heart was not only the heart of King David toward God; but the perfect heart of his everlasting heir: the Lord Jesus Christ...Himself.
John 1:10 He was in the world, and the world was made by him, and the world knew him not. 1:11 He came unto his own, and his own received him not. 1:12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: 1:13 Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God. 1:14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
John 1:33 And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost. 1:34 And I saw, and bare record that this is the Son of God.
John 1:37 And the two disciples heard him speak, and they followed Jesus. 1:38 Then Jesus turned, and saw them following, and saith unto them, What seek ye? They said unto him, Rabbi, (which is to say, being interpreted, Master,) where dwellest thou? 1:39 He saith unto them, Come and see. They came and saw where he dwelt, and abode with him that day: for it was about the tenth hour. 1:40 One of the two which heard John speak, and followed him, was Andrew, Simon Peter's brother. 1:41 He first findeth his own brother Simon, and saith unto him, We have found the Messias, which is, being interpreted, the Christ.
John 1:45 Philip findeth Nathanael, and saith unto him, We have found him, of whom Moses in the law, and the prophets, did write, Jesus of Nazareth, the son of Joseph.
John 1:47 Jesus saw Nathanael coming to him, and saith of him, Behold an Israelite indeed, in whom is no guile! 1:48 Nathanael saith unto him, Whence knowest thou me? Jesus answered and said unto him, Before that Philip called thee, when thou wast under the fig tree, I saw thee. 1:49 Nathanael answered and saith unto him, Rabbi, thou art the Son of God; thou art the King of Israel.
John 1:51 And he saith unto him, Verily, verily, I say unto you, Hereafter ye shall see heaven open, and the angels of God ascending and descending upon the Son of man.
Daniel 2:44 And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever. 2:45 Forasmuch as thou sawest that the stone was cut out of the mountain without hands, and that it brake in pieces the iron, the brass, the clay, the silver, and the gold; the great God hath made known to the king what shall come to pass hereafter: and the dream is certain, and the interpretation thereof sure.
Daniel 9:21 Yea, whiles I was speaking in prayer, even the man Gabriel, whom I had seen in the vision at the beginning, being caused to fly swiftly, touched me about the time of the evening oblation. 9:22 And he informed me, and talked with me, and said, O Daniel, I am now come forth to give thee skill and understanding. 9:23 At the beginning of thy supplications the commandment came forth, and I am come to shew thee; for thou art greatly beloved: therefore understand the matter, and consider the vision. 9:24 Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy.
Daniel 12:1 And at that time shall Michael stand up, the great prince which standeth for the children of thy people: and there shall be a time of trouble, such as never was since there was a nation even to that same time: and at that time thy people shall be delivered, every one that shall be found written in the book. 12:2 And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. 12:3 And they that be wise shall shine as the brightness of the firmament; and they that turn many to righteousness as the stars for ever and ever. 12:4 But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased.
Luke 1:26 And in the sixth month the angel Gabriel was sent from God unto a city of Galilee, named Nazareth, 1:27 To a virgin espoused to a man whose name was Joseph, of the house of David; and the virgin's name was Mary. 1:28 And the angel came in unto her, and said, Hail, thou that art highly favoured, the Lord is with thee: blessed art thou among women. 1:29 And when she saw him, she was troubled at his saying, and cast in her mind what manner of salutation this should be. 1:30 And the angel said unto her, Fear not, Mary: for thou hast found favour with God. 1:31 And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name JESUS. 1:32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 1:33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
Acts 1:6 When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel? 1:7 And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power. 1:8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. 1:9 And when he had spoken these things, while they beheld, he was taken up; and a cloud received him out of their sight. 1:10 And while they looked stedfastly toward heaven as he went up, behold, two men stood by them in white apparel; 1:11 Which also said, Ye men of Galilee, why stand ye gazing up into heaven? this same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen him go into heaven. 1:12 Then returned they unto Jerusalem from the mount called Olivet, which is from Jerusalem a sabbath day's journey.