Yes, but it's good for the prison-industrial complex and their vested interests, and that's why it's done.
Sadly, this is exactly so.
It seems most of our government decisions are being made based on the legalized bribery of our state and federal legislatures, for the purpose of increasing profits to the economic conglomerates that pay the bribes. They don't call this bribery, but that's what it is. And the result is that our government is making more and more irresponsible decisions that inevitably harm the general public, just to favor the wealthy elite.
And the reason they get away with this is that unfortunately, it's very easy to stir up people's animosity toward others, and get them to approve of harmful social policies so long as people think the harm will be done to someone else. Someone that we imagine "deserves it". Like poor people, and ethnic minorities, and homosexuals, and Muslims, and "pot-head hippies", and basically anyone that we like to imagine ourselves as being better than.
Using this innate animosity, turned against each other, these conglomerates get us to approve policies that harm our society in all sorts of ways. And yet when someone tries to point this out, they'll be harangued with insects and idiotic rationalizations by the general public because the alternative would be that we would have to admit that we're being played for fools by our own prejudices. And we'd much rather insult our neighbor that admit to that.
So you are right, it's nonsensical for someone to be put in prison for possession of an ounce of pot, and that these idiotic laws exist because there's money to be made incarcerating people, and the people making that money can bribe their legislators to write these idiotic laws and get them passed. But we are the culprits, too. Because they play on our own stupid prejudices to get us to let them get away with it. And we do let them, and have been letting them get away with it for decades. And as long as they can keep us hating each other more than we hate them for robbing and abusing us, and for destroying our society in the process, they will continue to get away with it.
Welcome to the Unites States or America, a land ruled by willful ignorance, spite, and greed.