You've led a sheltered life.
Trigger stops were standard for a while on a lot of guns, mostly on K-frames guns as I recall, like 15s, 19s, 67s 66s etc. At lot of the LEOs didn't like them because if adjust too tight or if it came loose and forward, it could tie up the gun, so a lot of departments removed them. You'll find used guns now with them still on or a lot of them with it removed and just a slot there.
Hope that helps some.