Well, withholding useful information from an employee can weaken the business as much, or more, than the employee. Given that business advantages are relative, that could potentially balance out. Conversely, the employees ability to work at will is an out-right advantage, so I'd argue that the employee still comes out ahead.
Additionally, these non-competes are often used in business where no meaningful additional data is shared, such as in the Dental field (e.g. they can't not share their clients with Dentists they hire, regardless of non-compete status). You may argue they would choose not to hire an associate in the first place, but then that leaves clients on the table for a new practice anyways. (empiric data would be a god-send)
Additionally, these non-competes are often used in business where no meaningful additional data is shared, such as in the Dental field (e.g. they can't not share their clients with Dentists they hire, regardless of non-compete status). You may argue they would choose not to hire an associate in the first place, but then that leaves clients on the table for a new practice anyways. (empiric data would be a god-send)