Yeah, people typically go into salaried management to move up higher in the company. It's more of a stepping stone into a corporate position or store manager.
Money. When I went from a lead to a co, I got a nice pay raise. Over the course of 5 years I've gotten over $20,000 in salary, just being a co. That's money I would have never gotten as a dept lead. Also I earned more vacation and get way more "vacation time". That's an irony because I never get to use it...but it's there on a sheet of paper for me to look at. If you stick around long enough and become a unit manager, you'll earn way more money and that's where you can make a very nice living.