Why do rollie pollies have armor?

Question

Ok so everyone knows rollies can roll up into a little ball with their special armor. But the real question is why? Why do they roll up when they are so small that the few creatures that would bother eating them eat fungus and stuff.(ex.beetles, roaches) Wouldnt they have changed over time and loose the ability along time ago due to evolution? Can someone please explain it to me?(i understand evolution and that stuff i mean about the bug.)

Answer 1

Rollie pollies are really terrestrial isopods, they are more closely related to lobsters than insects.  There could be things that prey on them, and it's a body plan that has worked for centuries, why mess with it?