Something I’ve been seeing recently is that there are many renters who are in absolutely no position to move because they are living paycheck to paycheck, have no savings, and as a result, cannot move into a new place. The new place requires at the least, first month’s rent and a security deposit (and many places require last month’s rent as well).
For expensive rentals like San Diego, this requirement can be very prohibitive. In cases where the previous landlord cannot return the security deposit, there’s no way they can find a new rental. So if they are evicted, they are essentially homeless.