It’s because there are financial and other accountability requirements unique to law firms (dealing with trust money etc) that are tied directly to the legal professional obligations of the person in charge of the firm.

Because lawyers occupy a quasi-public role in our legal system. They aren’t entirely separate from the system itself. The legal system depends on the enforcement of ethics and responsibility in a way that might be incompatible with a purely profit motive.

This point is arguable of course. On one hand legal services are expensive and often inaccessible for many. On the other hand more aggressive competition and consolidation has absolutely ruined society in a couple situations, medicine being the obvious example.

So there’s more than one point of view on this.

How many things have private equity ruined?

Now imagine you are given less than judicious representation by the only law firm in town.

Attorneys have a special status before the law. In particular, an attorney is legally required to act in the client's legitimate interests. If there is another person in the organization above the attorney and that person is also an attorney, the same requirement extends to them. But if that person is a random MBA or shareholder, they have no such obligation, which creates a conflict of interest.

Other true professions have similar but lesser requirements. Some leadership positions in a hospital require an MD. Not because the MD makes you a better leader, but because the position involves making medical decisions. In an engineering company, some decisions must be made by a civil engineer. And so on.

The requirements for attorneys are stricter, because the law is a special case before the law. While other fields exist within the system, the law is the system itself.

> Sometimes it works, sometimes it doesn't.

A lot of time it doesn't work, but more importantly, when it doesn't work the people who pay really can't tell. Law and medicine are very complex and ultimately are near total trust industries. When I go to the hospital I relinquish complete control to a bunch of people I don't know. Often literally - I could be under general anesthesia and couldn't fix the problem myself even if I wanted.

If the healthcare outcomes are worse in pursuit of a small increase in profit, I, the consumer, wouldn't know. There's so many corners to cut and I think a lot of them you could cut with only a small loss in quality. Probably nobody would notice.