Asking how long a feature will take is like asking how much it will cost to renovate an old house. Nobody can know for sure but you as an expert can give a better estimate than most other people. Nobody just asks a structural engineer to just build a house and that costs don't matter.

Why is that "wrong" estimate so important? Because business people do not see the real cost associated with features. They can only guess how many buttons you need to add to the UI. In order to build good products they need to weigh feature benefits against engineering costs. Even if the cost is wrong, it's about the magnitude compared to other options.

If business people get annoyed by missed estimates they don't understand engineering estimates and how to use them properly.