Why X essays just mean they want to know that you’ve looked them up - you know which journals you want to edit for/try out for, which professors and classes and course tracks most interest you right now, which extracurriculars caught your fancy, etc. Do a little research, and if you’re feeling ambitious get a copy of some of their law reviews and/or read some writing by some of Michigan’s fancier faculty. Googling Dean Caminker turns up some good stuff; the “entrepreneurial law” project looks current and interesting.
“Why X” statements are about why you want to go there, not just what you’d bring there. Make sure your statement is well-informed about Michigan and not just a ctrl + f/replace job.
This framework sometimes helps: These admissions essays are not contracts. Do not be dishonest, but be expansive, at least at first, while you’re drafting. What is absolutely everything you would want to accomplish at Michigan, in the best of all possible worlds? Think big, then get real as you edit.
What you bring to any law school are your enthusiasms, dedication, intelligence and genuine interests. You need to marry those to what Michigan has to offer.