Why do people get into relationships just for the relationship?

This has always confused me. Former crush got with a girl at the beginning of last year and this year but never past that it seems (I planned on talking to him too!)

I know other people in my school and likely other schools do it too. My question is why? Why do people do this? It seems like a waste of time ngl… I’ve heard so many stories of people getting expensive gifts for their significant other only for them to break up the next week

And no, I haven’t been in a middle/high school relationship