Great points. Though one tangential thing is - MBA school is largely not funded and I believe this largely cuts out the ability of people with MBA's to be in a startup at the early phase. I do not doubt the fact that a lot of MBA's and lawyers are very smart innovative people, just that the cost of their education often undermines their ability to take risk.
That and life stage. By the time you graduate from b-school a spouse, family and house are coming soon. The years in which one can earn ramen wages are precious and b-school takes up two of them, often at what might otherwise be your living expenses vs experience peak.