Where are you seeing that? Aren't the rules universally applied with the only exceptions to
Franchisee-Franchisor or and Non-Profits?
It's a reasonable argument IMO, and to your point, that is one of the most frequent complaints we hear from companies on the labor side. They invest a ton of time and money, but labor is more fleeting than it has ever been.
That being said, I would simply say - that is on companies to: 1) vet the applicant and their intentions/motivations during the hiring process, 2) provide a market competitive wage and benefits and 3) provide a better culture than others (2 and 3 are in no particular order and overlap).
In your example, it sucks for small and medium-sized businesses, in particular, as they are leaner and cannot afford to invest that time and energy while losing individuals. But, that's part of being in a free market. Free markets shouldn't apply to certain principles, but not others.
Most importantly, the enforceability of such a non-compete for a hairdresser was never realistic to begin with. If there was no extraordinary benefit or compensation received by the hairdresser, there was no way a court was going to enforce it.