according to a theory named.. mhm i cann't remember its name but it states that there are various levels for the desires of a person & the levels are as follows:-
So basically, when a person has food,clothes,home,security of its belongings the next thing it searches for is a mate to end its lonliness to enjoy & live this life more independently,therefore it hunts for love.
Did you get what am trying to explain? lol