They do to a small extend now. I've also read that some large law firms are making an arbitrage play by opening offices in low cost of living states. What they do is open an office in say, Tennessee, offer people who went to mid-level schools, $50k/yr to work 40-50 hours per week on a non-partner track job, and they do some of the lower skill/lower value stuff. They earn a comfortable living and are happy to do it. The firm makes some profit on it, so the partners are happy.
I work for a company that offers many products for attorneys/law-firms, and talking with my customers they are hiring again, surprisingly.