Maybe you wouldn't but tons of labs, research groups, etc would shell out for one. Allows people to use Unix tools but doesn't makes the biologists unnecessarily scared.
I'm only half-joking. I've seen a lot of wasteful spending in government and medical research divisions on Mac Pros (this was before the garbage can design) for precisely these reasons. At my last research job, I got a beefy (at the time) Xeon 24 core Mac Pro with 3 Tesla Nvidia cards as my work station. Really couldn't complain. Was a super nice machine.
