maia....basically, it boils down to human nature. LOL...I have written explanations of this until my fingers are little stubs.....but, alas, my efforts have not seemed to remove the pain from anyone who has asked that question!!
It seems that that question turns o ut to be mostly rhetorical, for most who ask it....
If you are interested, though, you can find my particular explanations by doing a search of my posts ...with the key words "romantic love" "romantic attraction"...."Mother Nature" "biology" "bonding hormones".....etc..
Go to the "search" button, at the top of the main page....
Yes, it does suck!
dandylion