The comments regarding proprietary or the license fee situations are correct.
ATi came out with Tessellation way back with the DX8 8000 series... it was called Truform. Very few games supported it. We now have DX11 and it's the "new rage" for game developers... why? Because now it's a standard in the DX11 specs. Since ATi already had a tessellation engine... it helped them get DX11 card first to market.
This is what has to happen with Physics. A split market between Havok / ATi and PhysX / Nvidia ain't gonna cut it.
I still haven't seen anything overly spectacular with Hardware Accelerated Physics. Extra particles... whooptiedoo. The non-hardware accelerated physics from old games like the original Far Cry or Oblivion seem to be good enough.
Anyway... until it becomes a standard with DX and/or OpenGL... or until Developers start really using it in a spectacular way... it will remain a non-issue towards purchasing a game, IMO.
Get your games from GOG DAMMIT!