Yes, I agree that there are many reasons why someone leaves chat quickly, with little explanation.

Sometimes I may not wait bec. the other person takes so long typing an answer, I'm not even sure that he/she is paying attention, or if they are watching TV, dealing with a child, went to answer the door or phone, etc.

So I think it's probably wise not to ***'u'me and especially not to infer that it's because of us.