That was mentioned in the second paragraph.
> It's a prisoner's dilemma because even though the economy would be better if non-competes were banned, any individual business makes more money by forcing employees to sign one.
Global warming is the same thing. If everyone pollutes, we all die and the world ends. Individually however, if I'm in a world where everyone is burning coal, I don't see any gain to setting up my own wind turbine. Meanwhile everyone who kept burning coal has a slightly better existence until we all die a horrible death. The flipside is also true, if I'm the only one burning coal in a world of wind turbines, I won't have a significant effect on the climate and I get cheaper energy.
The economic solution to this is regulating greenhouse gas emissions so nobody can gain an advantage from burning coal. We all live and businesses make more money (because Earth will still exist to make money on).
It's also possible to do this with non-competes. If a world without them is economically better, we need to put our efforts into banning them globally. It doesn't make sense to only ban them in the US or Canada, because companies can just outsource to where it's acceptable.
I think everyone does really. In fact, I'd say this is the "big idea" behind conservative fiscal policy as a whole. This assumption is the seed of it all.
Counter point, you are conflating each individual business profits and motives for the profitability of the economy and country. But each business doesn't exist in an a vacuum, but inhabits the same environment for getting workers. By making it easier to start new companies, and to compete, by banning non competes, the surviving business might actually be more profitable than the ones before.
Example: California doesn't have non compete, and it rules the tech world, with a lot of the more profitable tech companies there. While each individual company might benefit if it was suddenly allowed to do non competes, they benefit way more for being located in such a center for innovation.