It's meant to prevent investors from pressuring attorneys to prioritize profit over legal ethics. The thinking is that an attorney has their bar license on the line when making ethical decisions. If everyone's license is on the line they're likely to act in accordance with their ethical obligations. If a non-attorney invests in a law firm they could pressure the attorney to risk their license to generate more profit.
Accounting firms used to have the same rule (though they've relaxed it a bit to allow non-CPAs to own less than 40% or 50% as the accounting firms got more and more into "consulting"). The rationale is explained well here[1]. Large law firms are making a similar, though slower, transition to expanding their consulting services. Particularly with respect to data privacy and cybersecurity. I would expect the rules to relax over time.
The U.K. recently permitted non-lawyers to invest in law firms but it doesn't seem many investors have jumped in head-first. Law firms and accounting firms don't have much by way of "assets" so they can be quite risky. I briefly worked at Deloitte with a former Arthur Anderson partner. He was quick to warn all of the young staff about what a terrible investment his equity had been. One rogue partner can sink the entire ship and leave the rest without much ability to recoup the money they put in.
Which really cracked me up, having consulted with firms on the IT side and knowing so many lawyers, I can say that one's that put ethics above profits are the exception, and so lawyers already violate the basic reasoning for that law in the first place!
Just seems like an excuse to maintain a racket to me.
Accounting firms used to have the same rule (though they've relaxed it a bit to allow non-CPAs to own less than 40% or 50% as the accounting firms got more and more into "consulting"). The rationale is explained well here[1]. Large law firms are making a similar, though slower, transition to expanding their consulting services. Particularly with respect to data privacy and cybersecurity. I would expect the rules to relax over time.
The U.K. recently permitted non-lawyers to invest in law firms but it doesn't seem many investors have jumped in head-first. Law firms and accounting firms don't have much by way of "assets" so they can be quite risky. I briefly worked at Deloitte with a former Arthur Anderson partner. He was quick to warn all of the young staff about what a terrible investment his equity had been. One rogue partner can sink the entire ship and leave the rest without much ability to recoup the money they put in.
[1] http://archives.cpajournal.com/old/14469513.htm