People who don't pay their rent constitute a minor fraction of all evictions in SF. And when someone doesn't pay their rent there is an effective process for getting rid of them in a finite length of time. Most evictions in SF are not for this cause.
164 of 1977 evictions in 2014 were for late or non-payment of rent. Almost all of the rest were for pretexts classified under "breach of agreement" which tenants groups have shown to consist of things like parking outside the lines or cooking at night.
This is one of the things I really hate about California rental laws: there's not a standard lease. When I rented in Texas there was a statewide standard lease so there weren't weird clauses and other surprises.
The Rent Board's report notes that evictions for non-payment aren't required to be reported to them. So that's a floor, not a cap, on the actual number of non-payment evictions.
You can't sweep all 607 "breach of agreement" evictions away as "pretexts" – those can involve serious issues too, and it's a large category even in years like 2002-2004 when rents were declining. (That suggests it's not just a catch-all for wanting-richer-tenants.) There's also 349 "committing a nuisance" and 42 "illegal use" evictions. Some tenants are truly problematic!