A good many countries do not stamp passports on exit. many don't stamp passports at all. The US does not have exit processing of passports. Within the Schengen group there is not internal passport check at all, so nobody knows whether you've entered or left, say, Lithuania from France except by airline records. If you drive throughout Schengen they have not even that.

So, what's the big deal. I suppose you might prefer the Russian system with internal passports required for travelling around the country. Ah, I imagine not.