The housing market in the Bay Area is very different from the housing market literally everywhere else in the US (except in some ways Manhattan). Pre-listing sales are very rare outside of SFBA and Manhattan, and the vast majority of domestic residential sales (>70%) are of MLS-listed houses/units, even in major metros like Chicago and LA.

The "dog properties" don't get listed on MLS at all; there is a cost to listing on MLS and the dog properties generally don't generate enough interest to justify the expense (and usually don't even attract a realtor willing to invest the effort).