Purpose of creation

...i didnt create demons [l-jinn], men and women [l-nas] except that they serve Me [ya3buduni]..." [2:21]

The word serve [3-b-d] is explained by b. Abbas and many other famous tafsirs.  They all say "to serve" means " to obey".

Although one can obey unwillingly, the quranic ayah indicates a willing obedience as it does not mention animals and trees and angels and other beings which obey without free will (i.e. obey unwillingly).  This obedience is forced.  The ayah specifiy mentions l-nas and l-jinn. Two beings with free will.  Hence the obedience from these beings will not be forced.  It must come from the beings own free will.  A willing obedience.  And this only happens when the one obeying loves the one being obeyed.

Thus, to obey one properly with all your heart and soul (happily with full intention) happens when you love someone. 

Love = (willing) obedience = serve [3-b-d]

Thus.. according to the meaning of ayah 2:21
The purpose of creation
(The reason we..and other beings with free will.. were created)
Is so we could love God swt (and thus willingly obey Him)

You may ask..why didnt the ayah simply say ..."...i didnt create demons [l-jinn], men and women [l-nas] except that they LOVE Me ..."

The answer to this is the same reason the ayah didnt simply say......i didnt create demons [l-jinn], men and women [l-nas] except that they OBEY Me."

The word "love" may be misunderstood as meaning only to have the inward intention of love without having to act upon it.  Just as the word "obey" may be misunderstood as meaning only to have the outwardly action of obedience without any inner sincerity.  

The word "serve [3-b-d] nicely captures both meanings of obey and love, both the outward action and the inward intention

You might counter and say why then create the other beings and creation that have no free will?
These were created to allow the expression of love to manifest.  We cannot simply profess our love. We will be tested and see if we act by it in tjhis dunya...or if we do other than we say. 

Does a man who says to his wife he loves her...while committing adultery....truly love her?

Love is a seed whicb begins jn the heart (the jntention)
But it expresses itself in the actions
And the dunya / creation is a place for action / works