With med schools it doesn't matter, because that isn't your ultimate level of education. You still have post-grad training (i.e., residency, fellowship, etc.), and it is all on-the-job training, and you are evaluated by physicians from start to finish. With law school, there is much less post-grad training, so they tend to work a little more off of where you went. For example, here in austin, the law firms are full of UT grads. Its a top-10 law school, and the people doing the hiring are also UT grads. The majority of the rest of them probably went to law school somewhere else in TX. If not, they probably went to one of the "big name" out of state schools.
Also, with law, it is a much less critical job. That is, mistakes in law are typically corrected easily. All the young lawyers are asked to do is research stuff, write briefs, and other stupid crap. Then the boss looks over it and tells them to change whatever he doesn't like. And that's that. Nobody dies. So they can afford to base who they hire on stupid stuff like what school someone went to.
With medicine, they want people who can do the job. Stupid mistakes in the OR or ER can be fatal, so it is more important to base who they hire on how good someone is at their job. That's why you have to work hard and impress a zillion attendings, residents, directors, etc. from the very beginning. Once you've proven yourself to be a good doctor, over a long period of time, they give you a real job, and by that time, you are so far removed from your med school campus that it just doesn't matter.