Why the exact date of Laylat al-Qadr (night of power) is not specified?

*Why the exact date of Laylat al-Qadr is not specified in Islamic resources ?* I hear that people say the reason is to fill the last 10 odd nights with ibadah. But I think if it was so, Islam could just ask people for ibadah in those nights *for other reasons* instead. I think there should be something deep about this uncertainty of Laylat al-Qadr.