There actually is a decent amount expelled in gigantic jets, but the jets from quasars are relativistic (i.e., travel at a significant fraction of the speed of light) and escape the galaxy. Google "radio galaxies" and look at those images: they show jets shooting to megaparsec size scales (i.e., 10-100x bigger than galaxies), so that material totally escapes the galaxy.

That said, there is probably some material from quasars that gets mixed back into the galaxy - I think not that much, but honestly there's a lot unknown about gas cycling in the vicinity of rapidly accreting black holes. Nevertheless, even if all the accretion disk material got fed back into the galaxy, it would represent a truly tiny fraction of the galaxy's mass, much less than the material made by supernovae (our black hole is 10^6 solar masses, our galaxy is ~10^12 solar masses, of which ~10^11 is baryonic - so the black hole is a tiny fraction of the galaxy, and the accretion disk is a tiny fraction of that. my numbers here are super rough)