What do strut bellows do?

I recently replaced the rear shock absorbers on my hooptie I use to commute to work. When I took old ones out the bumper/bellows were in pretty bad shape. Since it is an old car used only locally my neighbor, who was helping me said that's it not that big a deal and to just install new shocks and throw away the old bellows. I am overseas and cannot find new bellows anywhere, I would have to order them from the States. Is the car safe to drive on new shocks with no bumper/bellows? What is there purpose anyway? HELP PLEASE!!!