Damnant quod non intellegunt

I suppose because, if Sirius was caught getting an unregistered wand for a twelve-year-old, he's more likely to get caught, and there would probably be more than fines. Anyway, then they'd have to explain WHY she wanted a wand, and what your average twelve-year-old witch just finished with her first year and coming from a magic-free background would even be able to do with a wand. It's not like Sirius knows this is her second chance at life. (I mean, what twelve-year-old is capable of becoming an animagus, especially over the summer. Harry managed it, supposedly, but Harry's special, and everyone knows it.)

LOL
I know. And the scary part is, I actually took a moment to consider the possibility. Ended up telling myself no in the end, but there you go.
(Secretly, he is. Bi, that is. It's impossible for Harry to be straight, he's just in denial.)