This is like people claiming that because a higher percentage of children of high earning parents become high earners, that they got an unfair advantage because their parents could pay for them to go to good schools, etc. That might be part of it, but having parents who are intelligent enough and have the attitudes and habits to get a high earning job means that you will most likely be more intelligent than average and have absorbed those attitudes and habits as well.
I don't doubt that those scenarios you describe happen, but I strongly doubt it happens at top research schools in any capacity that would be noticeable or affect anything. In fact, professors running the labs that I've encountered couldn't care any less about who you are, and way more about what you can bring to the table in terms of getting things done and published.
They have all been professors kids or friends of professors kids
Quick edit: I’ll also add that PIs project one face to prospective students and “outreach” students, like a high schooler is. Additionally, adding a high schooler to your lab gets you points for scientific outreach, which can help with certain grant submissions.
My (and that of everyone I know) experience with undergrad research was more like just taking a class with a professor, checking out their research papers, finding their research topics interesting enough, having a chat with the professor after the class or sending an email asking if their lab is looking for research assistants, meeting up with the professor to have an informal conversation to decide whether this is a good fit and whether it is a potential publication opportunity, and that was pretty much it.
Caveat to this: only talking about STEM fields, as I have zero idea how sociology/psychology/etc. labs hire researchers or even operate at all.
Sure, but the original comment was about the difficulty of getting published without being a child of an academic or an influentional person. Getting published as a 16-18 years old kid is insanely rare and unachievable for most, and I would agree that for that you might want to rely on hookups from parents. Mostly because it is so uncommon and rare, heavy majority of labs won't even be able to provide the necessary support for a high schooler to be productive in their research (exceptions apply ofc). However, getting published as an undergrad is very doable for most academically-minded students, and there are plenty of opportunities to do so at most research-centric colleges.
As for grad school, guess what's the most helpful item on the CV that professors and grad admission committees look at when deciding whether give an acceptance offer to a prospective grad student? It is their previous undergrad research and publication experience.
For example, admission to most top grad schools in biomedical sciences is only possible without quota if you have publications. Guess who gets published in their undergrad more often than others? Children of professors.
In the end the reality is pretty much everyone of socio-economic privilege gets one boost or another that's not available to other groups of people. That's why I don't get mad if some underprivileged classes get "unfair" quotas as alleged by the US supreme court. I didn't get mad that rich kids can get into Harvard without too much work, why would I get mad that an underprivileged kids can do that now?