Pretty in Pink

I grew up on "Ferris Bueller's Day Off," which to me will always be the best John Hughes movie. Seeing this a second time, I know why I wasn't in love with it as a kid. It's not as funny as "Ferris Bueller," and I'm not as into the characters. I especially don't understand the dramatic tension in this film. Blane gets with Andie, but then has second thoughts because he's worried about Steff's opinion of her since she's not rich, and then they get back together. But why did he care so much about Steff?