I would be upset too if I'd been invited to a birthday party under the impression that it was the kind where gifts are given and I'd actually bothered to get the person a gift, rather than a college style birthday party.

Consider though, American culture in general. People don't really bond so much and friendships tend not to be so close, at least that's the way it looks to me as a bicultural person. When people do engage in activities designed around togetherness, it can seem overdone or like un-kinking a hose. Weddings are big and flashy, even if the people don't know each other or have large families, parties can often be big and theatrical (if not completely artificial), sports have effectively supplanted the community atmosphere of regular religious services, etc.

People relate to each other in these ways because of the culture and to some degree, tradition. People like to feel that they belong, even if they don't always express that need or engage in it in ways that might be the most fulfilling. Figuring that out is part of the college culture too.