... and if they grew up poor and have no experience dining in a full-service restaurant, so they're uncomfortable and nervous... they won't get hired.
I think that unless the job involves dining with clients, so eating in restaurants is part of the job, the hiring decision should be based on qualifications, not how they handle themselves in a situation which is unconnected to employment.
(and before you think this is a personal issue, I grew up in Scarsdale and was graduated from an Ivy League university...)