It's completely unfair to pit an individual against a corporation. For the individual, a lawsuit related to a non-compete can consume their entire life for years while everyone working at the corporation has no real skin in the game. They'll go home and night and live their lives. Worst case they have to work late. It's not comparable at all.
It's better for a corporation to be wronged by an individual, than for an individual to be wronged by a corporation. So the law should err on the side of the individual.
To answer your question directly: frankly I don't see why not. Why can't the clients choose to change vendors? Is it not a free market? Are clients really going to change vendors just to still have the same sales rep?
A salesman doesn't exist as an island. He's selling products or services from a particular company, no? And if he leaves, he would then be selling products or services from a different company. Yes, maybe some clients will like the salesman enough to switch suppliers, but surely the fact that it's a different company with at least somewhat different products/services matters too, no?
Why are all these lazy entitled companies not pulling themselves up by their bootstraps and doing everything they can to keep customers?