The answers already made in this thread cover some of the problemsm but I'd like to add a bit to them...

Making co-responding morphs to those in V4, M4, the SM figures, etc. is a bit more complicated than you might think, especially when you consider the effects of multi axis movement and combined morphs in the base figure. The chance to get all of the possible combinations and factors right so the clothing performs perfectly is extremely small. The better constructed the clothing the less problems you will have but then again the time spent to copy/create ALL of that multitude of morphs = money (in the sense of $ per hour wages for the creator) so most of us try for a reasonable compromise of fitting to the most common morphs and to the most common poses, usually poses created with the LIMITS ON or a bit more, and hope that the user, if using extreme or unusual poses, can correct any problems with the morph tool, magnets etc.

Another factor is that clothing is NOT an exact copy to the topography of the base model. To exactly copy the mesh of the base figure is a copyright violation so you must use an original mesh (or start from one of the free use starter meshes). Because the meshes are not exact there will be some differences in the bending geometries and thus the clothing can bend in such a way as to intersect the base figure (poke thru). The fall off zone system used by Poser also has some affect in this area. JCMs are typically used to correct this but again the creator simply can not anticipate EVERY combination of morph and movement that the poser might use. 

Some things that might help is a dynamic collision system, similar to that in the cloth room but usable with conforming clothing, however this would greatly increase the computing poser/time needed. (Think of the sort of calculation/simulation used in the cloth room done after every pose move). True painted weight maps instead of the fall off zones would also help. I expect Smith Micro or DAZ to begin implementing these and other systems in the future, computing power has come a long way in recent years. I think they MIGHT have been added earlier but for the fact that re-writing the software to operate with newer techniques/ technologies will probably ruin any chance of "Backward Compatibility" causing a major negative reaction from the majority of the Poser community.

I would strongly suggest if you more realistic looking clothing, learn the cloth room. Naturally this won't eliminate ALL problems but if you take your time and learn it, and also take your time in the set up, you can get some really exceptional results.