Ever thought a colleague or some remote person you've seen around in the office, whom you'd usually rate as a sub-par potential romantic candidate in normal circumstances, was 'interesting'? That's just another way of saying that the person is actually attractive enough to you.
I think it could be an argument, and evidence if proven, in favour of biological processes at work when we think of the science of love. It is hard to think of any other reason why you'd consider a 6/10 person at work fascinating when you could easily find more attractive people on the train.
The reason why we end up making such irrational considerations, especially those who are not already attached, is that we are always seeking for potential mates. Because being in the office poses numerous issues, such as the lack of other potentials as well as the close proximity leading to possibly increased contact with that person, our innate need to seek a mate alters our psychology to convince ourselves that these other office people are potential material even though we typically would not think of them as so.
Because we can have a higher chance of getting to know a colleague or remote office person better compared to the good-looker on the train, a switch gets flicked in the head, inducing us to gain interest and perhaps encourage us to make a move. This could all just be biologically tailored to increase one's chances of getting a mate.