This is because perspiration causes corrosion. Frames should last longer with a daily cleaning. Dish washing liquid is probably one of the best cleaners for lenses and frames. Just a little drop on each lens does the trick. But, stay away from paper towels for drying.
Most paper towels are course and can scratch the lenses.
Employers can spend quite a bit of money keeping the employees outfitted in their planos. Of course, the employer is still liable if there is an OSHA audit. PPE must be worn where there is danger of injury. Therefore, most employers elect to pay for the eyewear in order to enforce compliance. It is thought that nice-looking, more expensive planos tend to stay in the employee's possession longer and that they take better care of them.