Better yet, why are they and their offices NOT subject to the minimum wage (not that anyone in a Congressional office makes less than that mind you . . .)
I like the system in the Texas legislature... amateur politicians that meet once every 2 years, and receive a salary of $7,200.
Actually, I bet there are a fair number of interns and campaign staff and volunteers that work for free. How about members of congress be required to pay the minimum wage for all of these people WITHOUT the option of raising their congressional operating budgets to pay for it (just like a business can't simply wave a wand and raise revenue to pay for increased minimum wage). Let's see how fast those ranks shrink and how loud the politicians scream when they can't afford to run a campaign or a congressional office.