Neonchameleon
Legend
It seems a more tame order to tell people that we will be playing PF or AD&D, than it would to tell them we are playing 4E. There is a closed set of parameters to play within PF and the other older systems while the edges of 4E and 5E seem like they are ever expanding.
Really? In 4e when DMing I insist that characters are created through an up to date character builder. And after that the only thing I worry about is that they fit the campaign. As DM I don't care - I just use new math for monsters (read: eighteen month old math).
Now let's take Pathfinder. 4e is balanced overall and balance problems can be fixed with minor tweaks. Now imagine that I ask for Pathfinder PCs and the following turn up: Wizard, Druid, Gunslinger, Bard, Monk (all competently made). We gonna have a problem. The Wizard and Druid will almost certainly rock, and the Monk and Gunslinger will almost certainly suck. So who made any sort of mistake? No one at the table. Everyone fitted the campaign concept. Everyone designed a character they wanted to play. No one set out to break things or otherwise turned up with munchkinery.
In PF the parameters may be more static (they aren't noticeably; splatbooks like Ultimate Combat are still being published) but more of them (like power level as well as theme) need to be set by the DM.