Also, messing around near people's homes tends to illicit a primal response.
If airbnb hosts aren't paying taxes properly, then the hosts are committing a crime, not airbnb. Cities may want airbnb to collect taxes on behalf of hosts, because it makes enforcement much easier. That's a reasonable thing to want. However I don't see what conceivable jurisdiction Palm Beach county has over Airbnb that would enable it to coerce airbnb to collect said taxes. Accordingly, I can't imagine why anyone in airbnb's position wouldn't sue, in order to avoid the formation of precedent that allows every municipality in the country to impose whatever requirements they want on airbnb.
You may think airbnb is a net negative for many communities, and you're entitled to your opinion, but that's not evidence that crimes have been committed.
As for why US Attorneys and State AGs aren't bringing criminal charges, probably because they are actual lawyers who understand that you would have to provide evidence that a law has been broken.
And tax evasion is a completely different topic, that is not why Airbnbs are shut down. Every industry has tax problems.
There's also the meta level issue that holding site operators responsible for the actions of their users is a very slippery slope. Anything that chips away at the communications decency act could have terrible effects for the internet as we know it[2]. For example, as it currently stands if I were to libelously claim that Paul Graham has a meth lab in his basement[3], I could be charged with a crime, but not HN. If the CDA were weakened, blog operators could be liable for comments posted on them. I don't think anyone reasonable wants that.
I think SF's law did a good job balancing things - hosts need to be licensed by the city (the app lists their license #) and can IIRC only lease 90 days out of the year. I looked at a recent receipt for a stay, and they even collected taxes.
[1] https://www.eff.org/mention/making-civil-liberties-case-airb...
[2] https://www.sfchronicle.com/business/article/Airbnb-HomeAway...
[3] To be clear this is a hyperbolic example, and I have no reason to think PaulG has anything illegal in his basement :)
Another problem is that the proliferation of this practice seems to be disturbing the already tense situation on the housing market. Meeting an odd couple from the other side of the world is fun. Realizing that you can't find affordable flat to buy in a city because a significant portion of it is scooped up for renting and short-term leases - that drives up societal discontent.
Fuck the locals, there's tourists that want to enjoy the sun in the summer and arabs that need to invest their petrol dollars.
You don't make a lot of money through AirBnB if you are keeping the place empty.