I do too. It's a combination of a lot of things.. I rarely use things "as is."  For characters, I combine different faces and morphs from different characters packs to get what I want, and the skin from something else entirely..  I use a lot of my own clothing models, and I do a lot of custom morphs on things like hair to get just the style I want..

The beauty with poser is that not -everything- has to be done from scratch.

For me it's necessary to do things like these if I want the image to match the vision I have in my head.