Why is it that if I look at my watch to check the time and then seconds later somebody asks me the time, I have no idea what time it is and I instinctively check my watch again in order to tell them?
It'e because you make a mental note of the time in relation to what you are doing - maybe you have to be somehere within a certain time, but you do not register the time per se in a way that you could advise someone else, so you ned to look again, register the hours and minutes, and then advise whom ever has asked.
It could also be a body language thing in that you need to refer to the "evidence", in order to supply believable information to the person asking you. If you just told them the time without looking at a reference point, they might just look at you in confusion and disbelief!
It's the same as telling someone there's a phonecall for them and gesturing with your little finger and thumb to your ear, you shouldn't do it but you do.