Dynamic clothing does have an objet file, but it's embedded in the prop definition. You can export a piece of dynamic clothing from any animation frame to an object file. Conforming is more poplular for 2 reasons. First, it works in both P4 and P5, while dynamic only works in P5, and second because you can create more complicated meshes for conforming clothing. Conforming clothing works great for heavier clothing too, like jackets, or very tight clothing like form fitting pants. I'll often design a piece of dynalmic clothing, drape it, then convert the resultant object to conforming clothing. It can really help fitting the clothing to morphs too. Both have their place.