It gives you exposure to the very interesting problems industry has that require technical solutions. It's a generally broadening experience. If he's an academic, it puts him in a better position to advise his students on career paths. It's high- energy, and decisions are made promptly. Of course, it is the rare scientist who gets to receive these benefits.
Few corporations have scientists as directors.
Generally, in order to be considered suitable to serve on a board of directors, a scientist must have established a national reputation on the basis not only of scientific achievements, but also of administrative and managerial skills. Furthermore, it helps to have spent a good portion of one's career outside the ivory tower. They are legally responsible. If a company is well run, these responsibilities can be exercised during the regular board meetings, which are usually held quarterly, or at most monthly. But that's unusual.