Cameras are problematic for AirBnB due to the tremendous scam potential. Consider these scenarios:
1) I'm a scammer. I stay in an AirBnB. Before I leave, I conceal a small camera somewhere in the room, and proceed to make a big deal out of "discovering" it. The room is refunded and the host is penalized or worse.
2) I'm a pervert. I spend the night in an AirBnB. Before I leave, I conceal a small camera somewhere in the room. I get off by watching the resulting footage, get paid by selling it, or both.
3) I'm a renter. I spend the night in an AirBnB. In the morning, I find the camera left by Pervert #2, possibly months earlier. I scream bloody murder. I get refunded, and the host is penalized or worse. Pervert #2 simply goes back to Ali Express and buys another camera.
There are probably numerous other variations I'm not devious enough to think of, all of which leave the host holding the proverbial bag.