why didnt britney like him as a bf?

Alex wasn't interested in having him as her BF because she wasn't going to stay in Detroit for long and Jimmy wasn't financially dominant/stable. She did see potential in him to be something greater than what he was dealt with in life presently, and it was enough for her to just hook up and get a quickie. But overall, yeah, she just couldn't see herself being in a relationship at all at this moment in her life where she herself plans to move out of Detroit and pursue her dreams in NYC and being with someone from the gutter.

His wealth / social status