I'm completely fine with what you said since you are entitled to your own opinion. As such, I will not brush aside your opinion, but I have my own views~. :P
The answer(s) I give are based on logical reasoning and are not held back by any emotional reasoning. The heart makes dumb decisions, fact. I'll start off by saying that as you grow to know a person, you become more and more fond of them, to the point where you want to meet them everyday, which in turns leads to 'love', supposedly. If you were to stop seeing them or stop hearing from them, what do you think is going to happen? Pretty simple really. You would either choose move on(to another person) or you would want to see that person even more. The first option can be seen as the more logical choice to make. The second choice, while not exactly illogical, it's not the choice one would normally make. The reasons why you might not want to move on and instead want to see the person again are because: you are just plain stubborn, keeping to a promise, and/or have gone past the point of liking them and it has become an obsession but you do not realise this because your heart tells you that you 'love them'. There's a saying, 'One can not know loneliness if he was alone to begin with'. <- Not sure why I said this, except that I wanted to make a relation to what I've just said but can not remember.
When you said 'i actually completely agree with that besides when you said attraction is based purely on physical appearance. it's true that it's the initial attraction, but you can't stay attracted to someone purely based on looks, I agreed with this to some extent. The reason why you can't just be attracted to someone based on looks is because it can only last so long. As people start ageing, looks slowly start to die out for some people. Think of it like this, hobbies can exist in any way or form. Love is nothing more than a hobby. You choose to love someone at first because you are physically attracted to them. If you're still enjoying said hobby, you will still maintain this relationship, else you'll move on until you're satisfied. In the event that you are still with the person, high chance that you would want to settle down with the person, make love, and maybe have a child too. Over time, you will end up coming into many disagreements with each other. Your views on your partner may never be the same as it was before. You will have a very healthy love life early on in your marriage but over time, this will slowly die out. At this point, staying with your partner isn't something out of love but is dependant on how much one can tolerate the other. As long as both partners are committed, they will stay with each other. As I've said, this is not out of love but how much they can tolerate. Love is merely a façade to cover up how much one would be committed to looking after another.
A person will most likely stay with another in a relationship because they have nothing else to do. They will probably try to rekindle their love life/spark for each other. Once again, out of boredom.
There's a story (this is a true story by the way) where a man and woman were in love with each other. The woman had cerebral palsy. Even so, he married her regardless of her disability out of what was called 'love'. They stayed together for a few years but her body's physical condition kept deteriorating and the speed of deterioration increased in the later years. Although he continued to stay by her, he wondered if his course of action was really an act of love her instead of an act of sympathy. In the end he was unable to stay committed to the relationship and left her since there was nothing he could do.
The topic of girls(by girls I don't mean what type we like but this is often the focal point of the topic), marriage, love are something of discussion between me and my friends from time to time and the conversations can get really deep to the point we talk for hours. I feel like I may have missed out some vital information since this is a topic I like to talk about face to face (or it could just be that I'm forgetful). Once again, this goes against what my heart thinks, but my heart is stupid.