I agree with you -- I never participated in these science fairs myself, but I attended a couple of summer programs where the majority of my cohort ended up submitting to these contests. The vast majority of people I knew who submitted (a statistically significant sample ~50) either seemed to have parents who worked in academia, or lived near a university, or just came from an incredibly privileged background (east coast new england andover/exeter or west coast harvard westlake). "Talent search" isn't quite right.
On the subject of whether the children who are involved end up doing real science -- I think they do, or at least they get a inkling sense of the research process. But aside from the difficulty of ascertaining the limits of human knowledge, they are also protected from the very real logistical aspects of the research process. Mostly, their papers don't get submitted to journals. Mostly, they won't be writing grants to fund their work. Mostly, they don't really have to join a lab for the next N years and develop significant working relationships with their peers and advisors.
On the subject of whether the children who are involved end up doing real science -- I think they do, or at least they get a inkling sense of the research process. But aside from the difficulty of ascertaining the limits of human knowledge, they are also protected from the very real logistical aspects of the research process. Mostly, their papers don't get submitted to journals. Mostly, they won't be writing grants to fund their work. Mostly, they don't really have to join a lab for the next N years and develop significant working relationships with their peers and advisors.