Regardless, they are fun to play with. When disturbed, they roll up into a tight ball, allowing their armor to protect their soft underbelly, head and many legs. They will remain in that defensive position until the threat is believed to have faded, which can be a long time. Their defensive, balled-up form often outlasts the interest of overzealous children.
They are considered primitive creatures, but they have an important role in the soil ecosystem. They are a food source for insects and arachnids. Their own diet of rotting organic material like leaves and wood mean they help cycle nutrients through the food web.
They can be found wandering under rocks, wood piles, fallen trees and other moist places where decomposition is likely taking place.