Why does Holden feel sorry for Lillian Simmons?

Holden feels sorry for Lillian because no one likes her.

This waiter was waiting for her to move out of the way, but she didn't even notice him. It was funny. You could tell the waiter didn't like her much, you could tell even the Navy guy didn't like her much, even though he was dating her. And I didn't like her much. Nobody did. You had to feel sort of sorry for her, in a way.