The technical/science degree to MBA path is there for a reason and is extremely common. A lot of people work in a technical job for five years and then decide that they'd rather move on to management then spend the rest of there careers as programmers, engineers, biologists, etc.
If there was an good enough reason for a business undergrad to pursue a masters in CS or engineering, you'd probably see more of it. However, there really isn't. I don't know any marketing undergrads who just decided to get into quantum physics because it would help their career path either. It doesn't mean they can't, it just means there isn't a practical reason to do so.
There are MBA's who shouldn't be involved in startups just as there are PhD CS's who shouldn't either.