Is that, all too often, they are completely one-sided.
When I need something done, answered, actioned, or otherwise handled is almost certainly not perfectly aligned with how you would like to accommodate my request, (or to spend the time to take a decision to actively not accommodate the request).
My, 'I need it by the end of next week' has to be translated into the language of your workflow, capability, availability, and most importantly, that mental list of the things that are ranked in order to their importance to you, (and that I almost definitely am not aware of).
I can ask you if it is reasonable if I can have that thing by 'End of next week', and you will likely tell me 'Sure, not a problem' because when looked at on a Monday or a Tuesday 'The end of next week' seems like forever away from now and the commitment to deliver seems so far afield from the promise that I would think you kind of incompetent if you simply said 'No'.
I think a better question than 'Can I have this by the end of next week?' or its close equivalent, 'About how long will it take before you can turn this around?' would be, "Where is this item on your priority list?' or 'Assuming you had everything you needed to work on this, when would you actually, you know, start working on it?'
I think it is much more important for the requestor to know how the person being asked to do something actually has the item prioritized and importance-ranked in their own mind than the often irrelevant 'How long will it take to complete?' angle.
It almost never matters how long something will take to complete.
What matters is how motivated you are to start.
Have a great week everyone!