And run carpools would be a fair comparison.

And that would impact performance enough that the NFL player would be out of a job.

Salary is a fixed regular payment. Conventionally and socially it's also understood to correspond to the employee giving his employer fixed, regular hours. Sure there's a little wiggle room in the edges for both employee and employer. But taking hours a day away from work in a salaried position isn't consistent with that understood employer/employee compensation/commitment relationship.