If you are shooting competitively and somehow manage to go to slide lock (because you didn't/lost count etc) … AND … need to reload … It is nice to be able to release the slide with your weak hand thumb as you are extending the gun/re-establishing your grip.
Some people say they can slingshot just as fast but to each his own I guess.
Light recoil springs (for competition) I suspect were responsible for the appearance of recoil buffers and many 1911s will not slingshot with one installed (removes too much reward slide travel for the stop to fall down).
I have shot a 5 inch M&P in competition "a lot" … it is a first gen M&P and one thing I always appreciated was it's ability to release the slide by simply seating a magazine aggressively. It is actually an M&P core ... and when it has an optic mounted it is kinda tricky attempting a slingshot w/o paying attention.
Of course ... it "IS" poor form to go to slide lock on a stage but sometimes it just happens (lose count / take a chance on absolutely/positively making that "last" shot to avoid a reload on the clock etc) …
But when it did happen it was cool (IMHO) to watch it slam forward all by itself.
This was something that was "fixed" in the second gen M&P and many youtube/gun forum experts immediately materialized to correct complainers … "that it is a slide stop … not a slide release" … blah blah blah …
Of course … everything works when you have all the time in the world … so again … I guess … "to each his own" … BUT … it is irritating to have them get on their horses (sgt tactical) and dedicate their lives to telling every errant sole "how wrong they are" …
AND … if the practice of releasing the slide with the little thingie on the side … instead of doing a slingshot actually did cause any significant wear … who cares??
These are competition guns (not BBQ guns) and you might actually have to do some maintenance sometimes (although I have not yet had to do so on my high mileage rock island or M&P).