Why? It is in many places, it's very common which is why I asked. Leads to frustration for property owners sure, but it helps balance the market, gives some power to tenants, to enable a decent cost of living.

Ok I looked it up for SF: https://www.sftu.org/rentcontrol/

Indeed, there is a control of only a few percent per year. So how is RentBerry legal?

"If the owner re-rents before the 5-year period is up, the residential property must be offered at the same rent that the former tenant was paying (plus annual allowable increases.)" https://www.sftu.org/are-you-paying-too-much-rent/