Weightmapping will greatly improve that, but it has a lot to do with the edgeflow of the geometry as well (and the limitations of poser's rigging have to be taken into account as well). Topology is key to any believable posing and animation, and without trying to start crap over this or that or anything, I'll just say, that I have never seen a human Poser figure that didn't have absolutely atrocious topology.

It is understandable, to an extent, that Poser topology is done differently than most normal models, due to all the morphing, etc., but too much of it is just sloppy work, regardless of what company it comes from, they're all guilty of it. Properly laid out topology can still be morphed and shaped well, so that's not an excuse.

I've never worked in a full production studio, (there are none where I live or I would be pounding on their doors) and I know that studios take shortcuts too, however while I was in school, had I ever attempted to submit something that even remotely resembled the craptastic geometry that most Poser figures use, I would have been thrown out of school. We had a very strict Quads Only rule that would get you failed pretty much instantly if it wasn't adhered to, regardless of how attractive the model was. There are very good reasons for that, everything from rigging and animation to rendering is affected by it. Never anything more than 5 points on a star, and NEVER any stars on the center line, were other points we had to follow. Optimization.

It is definitely not easy to model organics in all quads, especially when you can't use stars, but a lot of the time it is necessary. Poser is much more lenient, but there's still no excuse for sloppy edgeflow.