There are certain schools that actively recruit non-traditional applicants, but most schools have a majority to significant proportion of their students coming directly from undergrad so I wouldn't say that there is "discrimination" against them. They may be looking for signs of maturity in terms of you understanding what you are getting into, but I think that they do that for non-trads too. An adcom dean of a top 5 med school once told me that he actually advises pre-meds not to defer years, because you end up with fewer years that you will be able to work as a physician since the training is so long.