tl;dr: Managers will get in trouble for approving something that fails, but not for rejecting something which, if they’d approved it, would have succeeded.

Also, peers are much better at evaluating your work than you are (you think it’s better than it is) or than your manager is (he or she is looking for the flaws in it).

Could we apply that to publishing? If so, other writers are going to be better than you, and better than publishers, at evaluating whether your book is likely to succeed.