I actually exchanged e-mails with the head of admissions at Duke on this topic. My one school sample says.... meet their LOR requirements or risk the consequences And, final_id, I am also twenty years out. Your prof LORs matter for the same reason your GPA matters. It helps answer the question as to your academic success record as an undergrad. It allows for a semi-level playing field with all the traditional applicants.
Actually, the Duke website says this: Academic References
"Two recommendation letters are required. The preferred method of receiving recommendation letters is through LSAC. References from friends, family friends, and relatives are strongly discouraged. Professors who have personal knowledge of your academic performance and potential should write your letters of recommendation. We will also accept recommendations compiled and submitted by a central reference system at your undergraduate institution. If you have been out of school for some time, you may substitute letters from employers or others who are well acquainted with your personal traits and intellectual potential.
A signature is required on all letters of recommendation submitted, preferably on letterhead."
So I think the key really is to have two really solid letters that speak about your intellectual and analytic strenghts... regardless of whether you are able to obtain those from profs or employers.