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.
Having a promised date lets you keep the opportunity going and in some cases can even let you sign them there and then - you sign them under the condition that feature X will be in the app by date Y. That's waaaay better for business, even if it's tougher for engineers.