"Its enough of a pain to carry the shorts around with me, let alone a complete outfit. What do I look like, a pack mule? My clothes don't just pop in and out of existence when I change---I have to carry them with me while I run. Pardon me for keeping my burden light. Does my being half-naked bother you? Jacob Black
The reasons he lacks a 衬衫 so often: 1. He doesn't feel cold so he doesn't bother 2. If he needs to phase quickly, it takes less time to take off a pair of trousers than trousers and a shirt 3. It's less weight to carry around in 狼 form, and possibly less to lose 4. If he does phase too quickly and ruins his clothes, he only has to replace one pair of trousers.