Entrepreneurial skill is a rare human trait. But they lift the rest of us beyond starting from scratch with flint and bearskins, so it shouldn't be dismissed just because it isn't universal. Have those same studies looked at accumulation of capital and infrastructural reinvestment in regions saturated with microcredit? I suspect a left wing bias that views the rising few with suspicion.
My definition is simply someone who goes into business for themselves as opposed to getting a job. Taken that way, most people will be entrepreneurial given a good enough reason; and it's far from rare.
Also, it's surprising how many people work full time and have small side businesses they run part time. I believe I read a report that said the majority of US businesses are part-time, one-person only.