Medical schools require a lot of volunteering and things like 'slinging hot dogs to pay tuition' don't count unless you grew up without clothes surviving on rabid dogs in the holler of W Virginia working the coal mines from age 8. We all know who has time to volunteer or do minimum wage healthcare instead of work the best paying shitty side job they can get: the rich.

It's set up heavily tilted so you have to be rich, or dirt poor enough for a sob story, or a desired minority. Even if you do volunteer a lot and are middle class, you probably didnt know anyone that could help you into the most prestigious positions. A middle class person of equal aptitude would likely go into something like engineering or law which have fewer class-signalling non-academic purity tests.