San Francisco is really funny one. You have some of the biggest tech companies in the world right along with homelessness and poop maps. You can't make this shit up if you tried.
As for banning things, the gov. is fully aware of the fact that banning doesn't work. That's the whole point. First you (the gov. ) create the problem, and then you (the gov.) come up with the solution, which usually involves the expansion of the bureaucratic machine.
Oh and they found out during prohibition that it made them rich. Many of the political "elite" families made their wealth from prohibition. So when prohibition ended they lost some lucrative business. Solution. Make more stuff illegal and start working in the black markets that are created.
And some people keep arguing in favor of expanding the power of the state even further! LOL The gov. is the biggest cancer there is, even bigger than actual cancer.