well, mine doesn't - I don't like hot drinks. So the answer may be that through years of tea and coffee your mouth gets accustomed (or numbed) to heat, and mine hasn't been given the opportunity to do so.
I wish I knew too Loosehead - I've been able to drink a cuppa straight out of the pot since I was small. People always ask how I do it & my mum always said I had an asbestos throat. Not sure if it's a bad thing to do.
I imagine it's probably the same as a chef who can turn over a piece of hot meat with bare fingers. The nerve endings must have retreated over the years and no longer react so quickly to the pain.