The roads are packed so you'll usually see a traffic report with them interviewing people taking a picnic on the side of the road, complete with wine and cheese of course. Also, its part of the draw. When there is a known crowd coming most of the hotels and restaurants pull out all the stops: foods, drinks, live entertainment. A lot of these seaside towns can be quite sleepy during the winter so its sort of a big deal.
And, quite a few of my colleagues have family that moved south for the warmer weather, some just head out to visit family.