Are you sure about that? You seem to missing any sort of a source.

Almost all AirBnB rentals in SF were illegal before 2015. [1] I'm not going to comb through every municipality in North America, but when your company's primary operations are breaking the law in the city you're based in, I think it's safe to say that you aren't particularly keen on following it.

There are no particular bylaws governing subletting in tenancy agreements, but almost all landlords forbid it. Mine does. Yours probably does, too. AirBnB has not, and will never do any due diligence in verifying that a renter's tenancy agreement permits short-term subletting - they prefer remaining ignorant of whether or not their units are legal.

[1] http://www.nolo.com/legal-encyclopedia/overview-airbnb-law-s...

Pretty easy search turned this up. http://www.investopedia.com/articles/investing/083115/top-ci...

There also exist services to ensure compliance - http://www.hostcompliance.com/

A quick google news search also turns up a lot of articles about cities banning / deciding on the legality of abnb.

Additionally, your post was likely downvoted because you dashed off an aggressive, cliched comment that could have been answered with less effort than it took to post to HN.