Whats the point of a Permanent Retainer?

Ok well a while back i was told that i will need a permanent retainer after i have retainers...yes i had braces. But the only reason i had braces was for surgical reasons. The dentist always thought it was cool that my teeth were so straight, and he thought i would only need braces until the tooth came back. Ok well i've had my braces for 3 years and finally got them off. I was told i need retainers and a permanent one. Ummm ok my mom never had no permanent retainer and her teeth were terribly crooked when she was a child. So why do i need one? I haven't noticed any moment in my teeth and i've had my braces off for 3 months now and finally getting my retainers. Can i ever get this permanent retainer thing off? My friends say it sucks because its hard to floss and brush around, a couple were suprised i even needed one! And im getting them on both the top and the bottom? Whats the whole point of this anyway?