It's not that they need accurate estimates is that often sales people want to share those estimates externally, so anything that takes longer due to unexpected complexity becomes an accountability issue.
There is a balance there. sometimes you need to sell on the next version's features to get enough now to develob that. Not everyone gets unlimited venture capital - and it isn't always a good idea to take it if you can.
Accountability is everywhere, but software managers are always looking for the silver bullet that would let them have a stellar reputation of being on time.