On the one hand I do find my own over-investment in their story (both during and post-BB) fairly ridiculous.
But on the other - pretty much all of Western fiction in every medium is based on the love story. And usually about young people (because procreation, parental influence, carving out agency, etc, etc.) Reality TV is neatly halfway between actual real life and fiction - I’d say our brains are wired to care.