We obviously gain something. We gain an increased supply of rooms available for short-term use on AirBnB (and corresponding lower prices). The landlord gains a

We obviously gain something. We gain an increased supply of rooms available for short-term use on AirBnB (and corresponding lower prices). The landlord gains a tenant. The tenant gains the margin between the rent and the AirBnB fees, in exchange for the risk of vacancy, the work of listing the property and managing the guests, and the additional risk of being discovered and having the lease terminated. The tenant has a stronger incentive than usual to maintain the apartment as impeccably as possible, pay rent promptly in full, and screen AirBnB guests to minimize risks, since the lease can be cancelled with little warning if they're discovered. There's clearly a demand in the market for AirBnB. The landlord could easily cut out the middleman and list the property there themselves if they wanted to. If they want to write lease to cut themselves a portion of the profits while letting the tenant do all the work of managing the AirBnB guests, there are probably people who would take them up on that offer as well. Yes, contracts might get some extra words, but they're not written in stone. We can read the words and negotiate to change them to our liking for the mutual benefit of both parties.