Lap time

Recently I have really gotten into laps. I never was a lap kitty, but I must say, they are very warm and comfy. BUT, I do not like it when my mom (or whoever else I might be sitting on) tries to get up while I am on them. And even if they gently try to life me up off of their lap, I dig my claws into their pants! Why do I do this? Also, is there an easier and less painful way to get me off of their laps? Thanks!