I do SEO for lawyers, mostly Family Law. I can tell you SEO works as in: Proven Measured Positive ROI, to the point I wish I was allowed to own a law firm. One thing I would say though is SEO should be one part of your marketing strategy but not all of it. You should have a diversified approach. Edit: Let me offer a different way to look at it. Does having a well organized website help turn visitors into clients? Yes…
The problem with SEO and why I have a grudge against the industry is past success by gaming google with PBNs has led to hoisting up a few sites that can dominate because of their past. Those sites used spam tactics, then ranked high, that led to actual relevant backlinks, google got confused, and now keeps them at the top for any new content. Others must also utilize these dicey methods and pour serious money into it to do well. At least nationwide. I'm praying for the day that house of cards comes tumbling down.
Until then, having a better site, with better copy (done by a professional writer not farmed out), and using Adwords typically is the go-to.