Physicians and nurses are not usually recruited from the general public. They belong to organizations which are targeted. They are offered scholarships for their last years of school in return for service. They have organizations which place them in positions they would like.

Walk through any medical or dental school and look at the bulletin boards. They are thick with recruiting posters. Those are more likely to come to the attention of a practioner than a TV ad.

Any medical student or graduate is extremely aware of the positions available to them. I can't help but think the ads you've seen are strictly pap for the masses.