Glory
The work, while tiring, can be very personally rewarding. You're basically creating a work of art every time someone sits down in your chair and gives you an hour to transform their appearance. Film is a visual medium, and there is nothing more visual than what you do.
If you're working on a film such as Alice in Wonderland, The Curious Case of Benjamin Button, or The Chronicles of Narnia, your work may be one of the most memorable aspects of the film to a movie-goer. This is certainly the case for a film such as Norbit, which the audience will mainly like to otherwise forget.