Accurate engineering estimates don't have good product/market fit. You can't get management sign-off on a project that you accurately state will take 4 years,

Accurate engineering estimates don't have good product/market fit. You can't get management sign-off on a project that you accurately state will take 4 years, so you will instead just have to maintain and extend the old solution. That's the case where there's no competition. In a competitive market for engineering estimates, the low estimator will tend to win the bid. Meanwhile, you'll experience high turnover in your engineers, because you rightly want to only do maintenance, and management doesn't think that you need to pay high salaries to keep the knowledge in house. So management doesn't want to fund projects with accurate estimates, and engineers don't want to give accurately high estimates for projects they want to undertake.