I avoid clingy people because I find them annoying. Perhaps a desire to not be trapped underlies that annoyed feeling.

I would not mind someone talking to me at work, but I do mind calls at all hours and always being needy.

My avoidance seems to come in more with people that I perceive as "dangerous" due to their anger. Rationally, I know they are not going to physically hurt me. But anyone who has an angry type of personality or is easily angered is not going to be my friend.