The product must be of rigorously high quality and quantity to get capital or revenue. Work hours are as long as it takes to generate the quality and quantity of product to compete in the marketplace of ideas. A scientist's work hours are flexible, but extend to any time of day and night, year 'round. Therefore the market model of science only goes so far. To protect the reasonably-pursued truth, there is tenure .
Tenure is a form of job guarantee.
A scientist with tenure can't be fired merely for being unpopular or unmarketable. But salary is still subject to merit review, which is largely based on market forces.