Fame
Ivory tower fame is of the footnote variety. The more citation references to your law articles, the more bonus points you get to your name. In reality, becoming a law professor is a good way for high-class and famous legal figures to cement themselves atop the legal pyramid. Many former judges, congressmen, partners at big league law firms, and other megalawmaniacs have turned to teaching once they've had their fill with their previous careers, like Master Yoda.
Unlike lawyers, the esteem for law professors is fairly high...in the eyes of the general public. Just think about how many fewer jokes there are about law professors than lawyers. Then again, the jokes from law students have yet to enter the canon.