Toilet Seat Covers

If a person is so afraid of germs that she needs to use a toilet seat cover, then why does she leave her used cover on the toilet seat for the next person to dispose of? You would think these seat cover users would do away with their own toilet seat cover. It's very rude to leave them for the next person. I'm sure the germ fearing people would hate to encounter a used cover when they enter go to use the toilet.