Because who else would live in a tower? It's only evil kings and sorcerers that live in towers. Everyone else gets tired of all the stairs.

But knowing what's likely to be in a tower is not knowing why it's there. Why, I know exactly who I am, but I can't say I understand how I got to be on this road.

[ Yes, yes, of course she walked here, entirely by choice. But if it were up to her, she'd still be in Prydain, and not all of the explanations for the quarantine had made sense. ]