The main users of retention holsters are duty holsters for LEOs and other security personnel.
I think everyone who open carries in a social setting should use a retention holster to prevent someone from snatching the gun. Gun owners have a responsibility to see that their weapon doesn't end up in the wrong hands. And of course nobody wants to get shot with their own weapon.
A good, properly tensioned Kydex holster is fine for concealed carry as it offers plenty of retention. I'd not want a complex retention device on a concealed holster. Trying to press a button or flip back a cover strap while digging under your clothing in a maximum stress situation is not something I'd want to have to do. IMO anything more than a thumb snap is too much for a concealed holster. YMMV.
Yeah. I've seen LEO retention holsters, the one where you use your thumb to depress a switch and it allows the gun to be drawn. They are cool, and I understand LEOs are always in danger of having their guns taken from them when wrestling with suspects, so retention makes sense.
But for most concealed carry scenarios, I think it slows you down on the draw.