It seems to mostly be an issue in the southern snow bird parks and typically if the rig looks in good shape, they "forget" to ask the age.
Never had the question come up outside the snowbird parks.
You don't say the condition of the MH when they asked. If it was in rough shape or a model that clearly showed it's age, that was likely what drew the question. If it does come up and you feel guilty, you might try something along the lines of, "it's a 1993 refubishmentment". If they look out the window and it looks in good shape, they will probably shrug thier shoulders and move on.