I feel like it makes them look more "human" or "civilized." I've always thought they looked weird with just fur.
This should summarize my view to an extent. Of course, there's also the idea that I just like using clothes as a manner of self-expression, and I'd gather that anthros, if exposed to clothing, would probably be inclined to wear them for just that reason as well. But, in the case of the cold-blooded and/or hairless, they would use them for many of the same reasons a human would. Personally, I think it'd all be up to the cultural influences, environment and exposure that would dictate their propensity to dress themselves. One has to consider that they would form cultures just like we did, and let's be frank here: no amount of fur would totally hide everything or keep them totally insulated and warm in every situation. Clothe-wearing habits would develop somewhere along the line.
That said, that's how I use clothing in my headcanons. Transference of a few human societal traits and unique twists to suit the species. Some have special garments while others have the same clothes that you and I have. For instance, dragons: their shirts and tops have straps or buttons with openings in the back for wings. Unless the wings are vestigial, they attach around the bottom, near the buttocks, so the whole wing fits. Making holes in your wings at birth just to fit a shirt would probably suck and limit the ability to fly properly.
I overanalyze things, I think.