Hate to say it but the cold-blooded theory doesn't work. Cold blooded animals -like reptiles - rely on the environment to regulate their body temperature. That's why you'll often see reptiles basking in the sun. Warm blooded animals - like humans- are capable of of self regulating, through sweating, shivering, physical activity ect.
The idea of clothes is to trap the heat already being created by the warm-blooded body. They would do nothing for a cold-blooded creature.
So...maybe it is to hide the seams?