I wonder how it is in various states, but at least where I live the actual plumbers get licensed, not the plumbing company. So what can they do to stop it? NDAs? Non-Competes? The state also takes a dim view on such things until you are paying someone a significant amount of W-2 money.
SEO? Brand recognition?
Well anyway, a few months ago I shared a table at a restaurant with someone that worked at a family office, and was buying up landscaping companies. I asked some questions in a polite and friendly manner; nothing too pointed or invasive. But came away with the idea that there is a lot of money out there looking for something to do, and not a lot of good ideas.