Homelessness might evaporate over night if just a small fraction of home dwellers opened their doors to those in need; but there's good reason why doing so is prohibitively untenable, and the solutions are more complicated than simply making a bed or couch available.

I don't think it's fair to claim that that who don't volunteer are virtue signaling slacktivists; they may simply believe the solutions must come from larger institutions than individual action.