Superstition, that's all! If you grab one of its tails then it puts a thousand year curse on you, but there's also all kind of stories about Ninetales. One I remember hearin' about growin' up was how each of the tails had its own special power, and it lives a thousand years itself because of how mystical it was.

[... So, you know, basic legend stuff. It's just a story.]

'Course, Ninetales only curses people that mistreat it, so as long as you're careful and it trusts you, you're free to pet it all you want! Brushin' their tails is part of the groomin' routine.