There's lots of reasons, RorrKonn. The sim time puts some people off; they want quick, and no dynamic sim really meets that demand (if they've multi-threaded the core exe, then maybe that has changed). Others have jumped into it and treated it like click and render, and neither is that, either. Then you get into the collision issues. The hair works best if there are low poly proxies to collide with, and not the high poly meshes of the figures and clothes. The cloth sim does an outstanding job of catching between limbs and in joints, where people figure that they can cheat since no one is going to see that area. And neither cloth or hair room has what one would call in depth documentation....at least not the kind that makes it easier to set a sim for silk or cotton, or arrange hair groups for best effect. And some of it is simple laziness. I quit counting the questions from those who've loaded a conforming outfit, tried to run a dynamic sim on it, and whined that the app was 'broken'. RTFM......or ask someone if the answer isn't there.

However, since DAZ is dipping its toes into the dynamic cloth feild, maybe we'll see more interest (although their solution is so limited atm, who knows....).