The wisdom behind not knowing which exact night Laylatul Qadr falls upon ❤
Ibn Qudaamah Al-Maqdisee (rahimahullaah) said:
“Some of the people of knowledge said:
Allah The Most High made this night unapparent (obscure) upon the Ummah in order that they should strive hard in seeking after it; and that they should find aspiration in worship when seeking to attain it.
Just as He made the hour in which the supplication is answered on a Friday as unapparent – in order that they should be plentiful in making supplication throughout the day.
Just as He has made His Greatest Name unapparent from amongst His Names; and His Pleasure in varying forms of obedience – in order that they should strive hard in all of them.
Likewise He has made death and the establishment of The Hour as unapparent – in order that the people should earnestly endeavor in performing actions – out of caution from them both.” 
 Mawsoo’ah Al-Fiqhiyyah vol 35 p.366
original reference can be found in Al-Mughnee vol 3 p.117