The proliferation of these overprotective practices reminds me of the proliferation of simpler practices we impose on kids like showering regularly and wearing clean clothes that we just take for granted now. The link in my mind is how you can pick most any practice that is common amongst a majority of the population today and look back 50, 200, sometimes 2000 years and you can trace it back to a minority aristocratic or ruling class. You know, like medieval kings taking regular private hot baths but this not becoming feasible for the rest of Europe until the last century.

Another commenter made an observation along the lines of you see overprotected children nevertheless succeeding (or failing up, depending on your perspective) professionally as adults. That would make sense if what we are doing is slowly handing down practices from the higher classes to lower. The failing up phenomenon is clearly highly correlated with the privilege you were born into. As everyone becomes relatively more privileged, then practices would radiate out and be institutionalized amongst more of the population, i.e., everyone would start overprotecting because as long as your kid makes it, worse case, they will be able to succeed via the fail up method.