Being a little disillusioned about the world these days I would assume this has a purpose. My guess is this: Booking.com already knows that they are fighting a losing battle against AirBnB. So instead of trying to win it seriously, they go to make the biggest profit they can out of their situation by strongly focussing on the idiots. With idiots you have two advantages: (a) they stay anyways no matter how shitty you…
Maybe I am wrong, but I though Booking also lists apartments for rent? At least in Romania, I know people that rent to tourists usually publish their offers on both websites.