They're notorious for living in towers, but high floors were not a sign of high status until elevators were invented. You put your servants in the penthouse and let them traipse up and down. (And then groused about the servant problem.) True, there are those who would deem a wizard a servant -- all that bookishness, not a good fighter in battle -- but any serious fantasy wizard would set that straight Real Quick.
Then, wizards have a few options. Flying, for instance. Or having their own servants doing the traipsing -- especially if they consist of animated wood or stone. Or conjuring food and other supplies. And letting those who wish to speak with them cope with the stairs. Would certainly help ensure that any requests are important.