It's not clear that anyone has the legal means to stop you from hosting your friends for free.

Besides, couch surfers typically stay in the same house as the current resident, and he/she has to maintain good relations with the neighbours.

The apartment adjacent to mine recently got turned into a short-term rental place. Most of the time there's no problem, but every couple of weeks an extremely loud group of tourists comes over and treats it like a party house, making tons of noise, blasting soccer games on the TV with associated loud cheering, etc.

Couchsurfing hosts generally don't give up their entire place to their guest(s), which is how the short-term rental market operates. According to the article, they explicitly legalized the situation where you're sharing a unit, but you have to pay taxes.

You are assuming that Airbnb hosts give up their entire place. I never been to any Airbnb where that was the case, it is anecdotal evidence but without presenting the numbers you can't really make that argument. On the other hand I was in CS hosts apartment alone. This is also just anecdotal evidence, but I think in this topic these details have nothing to do with outcome of that voting.

Of course some Airbnb hosts give up their entire place. There's a big button to limit your search to just those properties.

Airbnb shows 667 out of 918 rentals in Santa Monica are for the entire place, i.e. no host present. The vast majority of rentals there won't have an owner present.