They often import untextured and certainly without good Poser shaders. But they mostly come with textures you need for dashboards and lights. It's usually easy to load the textures and apply good Poser shaders (assuming you have them to apply or know how to make them.)

For the glass, paint, or chrome, you don't need (or want) textures at all. These are entirely one (or no) color and they shine according to the Fresnel equation.

I made this image from one of those obj files just the other day.

http://www.renderosity.com/mod/gallery/index.php?image_id=2553021

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)