This is a bit of a hyperbolic statement(I wouldn't classify most pre-meds as having zero work experience) but the key thing in all of this is is context. Many pre-meds come from very wealthy backgrounds. Others don't. ADCOMs do account to some extent for the background you come from; those who come from lower SES backgrounds and where it's clear they have to make ends meet every semester through blue collar jobs will have their EC's look at differently and from a different perspective from your generic pre-med who has both parents as physicians.
Work experience doesn't work the same way as artificially "boosting" your resume the way some might think a publication or program like Americorps might. It provides context for the lifestyle you've had to live, and can show certain skills you've developed(ie communication skills, team management skills, work ethic) that can be viewed in a positive light, especially if these become apparent in an interview. Work experience can be as "critical" or "not critical" part of your application as you make it and what it says about you. What people often mistake work experience and what it can do for you and where they are wrong is in thinking a) work experience can provide an excuse for mediocre grades b) that work experience excuses you from the responsibilities all pre-meds must show(clinical exposure, volunteering to demonstrate altruism) etc.
