It depends on the nature of the relationship if anything. If you view someone as a friend, it is much harder to be physically attracted to them in comparison to someone you experience love for.

Love, viewed from a Darwinian perspective, is basically an evolutionary and survival based mechanism, like many others, that is designed to push you in the right direction. The way it works is very similar to fear.

Why do you approach a woman you like? Evolutionarily speaking, you do it to stick your penis in her and make babies. Even the process of sex is designed to get you to reproduce as much as possible. Why is sex so fun? To influence you to have more of it and make babies.

Why are you stricken by fear when faced by a tremendous height or a cobra or darkness, and other stuff, and why are your physical abilities altered accordingly? One bad step and you're fucked by the height, the cobra can bite you and kill you so the fear pushes you away from it, and your eyes widen and other changes occur that enable you to an extent to get away from possible dangers in the dark.

It isn't a coincidence. Humans that don't experience those are broken, in a sense. We are guided by our 'coding', and how well it works solely depends on the environment it is deployed in. From what I understand, to some degree, it can mutate and adapt, according to what the needs for survival are, but, it still rotates around several prime objectives.

Not to suggest long distance relationships are bad or anything, we just aren't naturally inclined to participate in one. They came along with the rising popularity of the internet. Not that there weren't any before, but, they were far lower in number.

I can write an essay analyzing how the principles work in long distance relationships, but, whats the point, it'd just be a waste of time writing. Feel free to do whatever you want, consider this to be a scientific hydeservation.