At every place i've worked, people in marketing/sales are significantly better looking than in engineering jobs (by that I mean a significant number of people are significantly more attractive). The easy way to explain this is that being attractive is enough to get your foot in the door for a sales position. It also is worth noting that they are, on average, making much less money than the engineers, so it would be a resonable hypothesis that they are less driven to learn because they are good looking, thus end up in an easier job.