Why do Chat Reference Patrons Disconnect?

I spend a few hours a week working with the online chat service QANDANJ. It is very frustrating when you are trying to answer a question and come back to the chat and find that the patron has disconnected. What are the reasons for this?

• Are they so impatient and expect an answer instantly?
• Is it a technical glitch? - Maybe sometimes but not all the time
• Is the patron multitasking and forgetting about the online chat session?