What is the main reason though? The BigCo being too risk averse? Or employees having too much of a safety net? Or BigCo processes weighing the team down? A combination of these?
Edit: To clarify my last point, my assumption being that the point of InternalStartup was to allow deviating almost entirely from BigCo's approach to everything and that those people from OtherBigCo would be less likely to have that mindset.
It's that simple.