Front faces only - enabled by default

Sculpting, weight, color paint should have this masking option on by default.

Even experienced users can forget to turn this on for every brush/tool they switch to. (This is not a unified enabled setting so you can set it once for all brushes)

I know I can save a startup file checking this for each brush but is not that practical when I have to maintain and work with multiple startup files each with specific settings.