If I have responded to someone's posted question and don't get any indication that they've seen the response, I will check to see if they have logged on and had a chance to see my response.
1. Questioner has not logged on since they asked the question. I start wondering, why'd they ask if they don't care?
2. Questioner has logged on since I posted an answer and not said thank you. I think, what an ungrateful cad.