*nods* I think Sam is a very stubborn customer. He refuses to fix up his flat or move to a new one, after all (and we know from his reaction in 1x01 what he thinks of it!), right? So I can only assume that when he's bought new clothes, it's because he felt (reluctantly) that he HAD to. And he probably hated himself for it, because by doing so he was giving credence to the 'reality' of 1973.

(Thanks!)