They would much rather confidently repeat a date that is totally unfounded rubbish which will have to be rolled back later, because then they can blame the engineering team for not delivering to their estimate.
I've made your argument before, but realistically, much of the word revolves around timelines and it's unreasonable to expect otherwise.
When will you recover from your injury so you can play the world cup?
When will this product arrive that I need for my child's birthday?
When will my car be repaired, that I need for a trip?
How soon before our competitors can we deliver this feature?
"It'll be done when it's done" is very unsatisfying in a lot or situations, if not downright unacceptable.