I've read reports of how the thumb-break retention strap on some designs can enter the trigger guard and contribute to a ND on reholstering.
I think this is especially a problem with light trigger-pull, no external safety designs (Not Glock-bashing, but I believe they are susceptible to this problem, as well as some other similar designs.)
Of course, I read a report of some LEO reholstering after reclaiming his weapon from a courthouse locker and he managed to do the ND thing with a shirttail, so you apparently don't need a retention strap to do this.
I always read of the speed of draw issue, but I rarely read about this. And, if you consider how many times you are likely to have to draw and fire, vs. how many times you unholster / reholster for administrative reasons, the concern of what that thing might do
besides retain the gun might be valid.
On the other hand, if your lifestyle requires you to do the equivalent of cartwheels across a parking lot, you might need a retention strap.