My new cat likes me but hides anyway?

she's a year old and i got her over a week ago. she lets me pet her and purrs when i do, and she also nudges up against my hand, and rolls around, etc. but she always likes to hide. and i don't understand why she does that. whenever given the opportunity, she'll squeeze into some small crevice and hide under the bed. i mean, she's pretty used to me already, so why does she do that?