I don't think you can generalize things so cleanly. Every country and every airport makes decisions that make sense to them, there isn't necessarily any consistent set of logic for all of them. For example in CPH arriving non-schengen passengers mix with departing non-schengen passengers and can enter schengen by going through a passport check. No security.

But generally each region wants you to go through security at least once in that region. You would think Europe and the US could synchronize standards and expand the region to include both but then that would require separating passengers from Europe from passengers from other regions.