Probably because they've been taught either to "SUFFER FOR YOUR PASSION~!" or to not work in anything that's below you --eg a fast food job-- because that's insulting to one's dignity ("don't lower yourself"). Or both!

Ok yeah, if one studied something for a degree and is working in McD's, it feels a bit silly/insulting. But at least there's a paycheck and not a lot of stress involved, compared to just living on commissions. :\

(sorry if this reply seems snobby or rude. For some reason I can't explain my point very well today >_>)