Yeah, Marc will be along shortly to tell you why.
It's because a ninja bad guy could throw a pebble in the retention release mechanism, and you won't be able to draw your handgun before the other ninja bad guy snaps the gun off your belt like the cheap toy that it is.
Then he'll shoot you with your own gu...n... wait, how's he getting it out of the holster with that damned pebble in there?
Oh, wait! ninja bad guy would be highly likely to shoot himself because he would press the button IN,
and simultaneously pull his finger BACK, discharging the firearm and putting a hole in his split-toe Tabi shoes!
Good thing that pebble is in there!
ehh, maybe I got it all wrong?
Marc?