Ask HN: Why do big companies rarely hire people with 0 yrs experience as a VP?

I've been looking at some job ad's for positions which say "Director" or "Vice President" or some high level management. They always mention they are looking for someone with 10+ years experience,a resume the size of dictionary, and so forth. They never seem to be looking to hire anyone with 0 years experience but with a ton of motivation to try something new. Any idea why?

Companies like this spend billions of dollars to acquire companies with a culture which do the complete opposite of what they do. If they only spent those dollars starting a few divisions and putting a few "start-up" leaders there, they might create something cool. However, that rarely happens. Why?

Starting an "entrepreneurial" division in most big companies is insanely difficult. Why won't they allow that? Dollar for dollar, it would probably be cheaper if they create their own then buying successful startups.