We love because we cannot control our emotions that is why sometimes the things we feel are involuntary, sometimes people wonder why they feel things for people that they shouldn't and the reason why this is so is because if people can control the way they feel then love will be meaningless that means that people can choose to channel love to who they want and this will be definitely detrimental.
Now love is not just simple it is the most complicated illusion that you will ever know in fact even the human mind cannot fully explain what love is because it is very vast and people are still taking time to understand it like. Like you asked in your question, people can leave who they love because they've been hurt by that person now it doesn't actually mean they don't still love that person. Love can make you do things that are stupid this is because when someone is emotional it is very difficult to make use of their senses, it makes the perception clouded and you hardly see things for what they are that is the effect of love.
The reason why you asked this question is because love can seem confusing, someone can claim to love someone so badly yet they still hate them in physical it definitely happens even when it seems ironical love can be very complicated even we as human cannot fully explain the extent to which love can make us do things in some situation it can even make people commit suicide and that is a very dark negative side to love. So love is not fully explainable because it is very complicated people can love someone and yet they can still leave them
We love simply because of the fact that we do not want to be alone. We love because we want to marry the one who loves us and we love them back too so that we cam start making babies and plan a wonderful family.
We do love too because we want to stay happy in life.
Humans always need someone to lean on and confide in too, someone we can tell our problems ,someone who is transparent enough to tell us what they like and dislike in our actions. We need someone to encourage and motivate our dreams that is why we love.
We love because if we are lucky to marry the right partner, they can be supportive enough to let us find and achieve our purpose in life.
We love because we need someone to stand by us in trying times.
We also love because God is happy with a United family where mere issues cannot be a barrier to their love.
There are always bound to be misunderstandings in a relationship. Those misunderstanding strengthens the bond and make us realize how much we need to love people in our lives.
Matured minds can never separate because of little quarrels, arguments or misunderstandings.