Oh, I have fun, trust me. [Plenty of it, in fact.] But I mean, I can't abuse my powers. Imagine if I teleported myself any time I had to leave the house - I'd gain a hundred pounds and everyone would think I'm lazy.

[There are other reasons, of course, like toying with someone's memory or messing around with reality, but he's trying to keep her cheered up, not freaked out.]