I enable persistent scrollbars on any machine where I'm doing front-end web dev, so that I can better see what (some of) my users will see (not doing this has bitten me when it affected layout). But on my personal laptop I leave the scrollbars off. I virtually never drag them with the mouse these days and they just clutter my visual landscape; I'm glad the option is there to hide them (and dear god would they get in the way on the already-limited real estate of a phone screen).