lol, not all dev's want SSE enabled by default, because some have CPU's too old for it, and exactly how many serious dev's run code on over decade old CPU's, at 450Mhz and under, which don't have SSE? Likewise, the "retail" package they include in games will all have SSE1-3, most will have sse4.
They don't use it because 3 people out there code for pre P3 under 450Mhz non SSE having cpu's, the other 2billion people with computers are just **** out of luck.
My god, they can't even lie well anymore, and thats really bad news for Nvidia because thats what they've been best at for so long.
The thing is, I've been saying for ages, Physx does nothing other apps can't be writen to do, the reason Havok and other things don't get into quite as much detail is because its NOT required, not because there isn't the power to do it. Rroff can talk about realism but then physx is used in many situations where things don't interact well. INteraction is done via DESIGN, like paper/leaves going through Batman in one of Nvidia/Physx's "major titles" most of the effects simply aren't realistic and mimic, honestly, very very old style effects, leaves blowing around his feet, big whoop.
Physx for ages had obviously been purposefully design to run badly on CPU's so they could say/show how great it ran on a specific core, honestly they'd be silly to do otherwise, Ageia wanted to create a niche and sell hardware(well they wanted to sell the company to the first sucker who thought it was a good idea.....) theres little point creating code that will run great on other hardware making the thing that would make you the most profit pointless.
Even so the vast majority of what we see from physx hardware acceleration(which can clearly be done on the cpu as well if it wasn't crippled) is bonus effects that require extra gpu power to draw, after the effects have been calculated. Its STILL not anything fancy adding impossible to otherwise do in game primary physx's, like players interacting with doors and so on, as we've seen, Batman, one of the biggest "physx" games, doesn't use the hardware to have the character interact with the door, or fight, or bodys crumple to the floor, it deals with leaves blowing around, and a couple chucks falling off walls. Nothing we haven't seen in games for well over 5 years, and nothing thats not easy to do with little power cost.
They are basically pretty much standard effects removed, coded in poop to run badly and re-added for Nvidia cards only. None of its a massive leap forward, its just rubbish.