My wife has a PPS. You can remove the backstrap by sliding it down a bit until it disengages. This causes the striker to de-cock. There are two reasons (in theory) for this feature.
You can release the striker without having to pull the trigger. It's less trouble, of course, to clear the gun and then pull the trigger to drop the striker.
Also, since the gun is rendered inoperative with the backstrap removed, you could leave the gun loaded and carry the backstrap around with you.
The backstrap is made of polymer. If you attach and detach it repeatedly, would it wear out? Possibly causing it to come loose at the wrong time? I dunno. Hers is pretty secure so far.
If you otherwise like the PPS I wouldn't let this put me off.