This guys story is an example of a reasonable reason to restrict. Tons of horror stories like this. I would not be surprised "Airbnb clauses" become standard in rental contracts AND maybe even condo and co-op bylaws, depending on how the owners vote, of course, which will vary by building, some allowing, some not, but it should be a conscious decision, not a silent issue kind of thing. The clauses will probably forbid Arbnb rentals. If Airbnb rentals are allowed, the landlord and/or condo/co-op association should get a cut of the money. Administrative costs, extra hassle, risk, insurance, and, yes, a share of the profits for enabling it.