If you are a young startup, you get the luxury of making bold changes in production because people are probably paying a good price and getting lots of funtionality and most people can live with the odd bug, as long as it gets fixed quickly.
If you are e.g. IBM, you have massive codebase(s) developed over many years that are fragile as a spiders web. Sure you can dive in and attempt a fix but that is both more risky than your much younger and consistent startup codebase but also affect not just lots of customers but also your reputation. Any problems with the software and your customers are suddenly asking, "why are we paying a premium for IBM when we keep getting these bugs?"
Someone also mentioned compliance. The bigger you are, the more likely someone will pre-emptively prove your compliance (or not). Why? Because they are also corporations and don't want their reputation to suffer.
Personally, I think those that thrive in startups never do in corporates and vice-versa.