And it’s not like the parents would actually kick them out if the missed a month’s rent.
You will NEVER build your credit for the times when you need it (buying house, unforeseen circumstances, a car that costs more than $15k, and I’m not being an asshole, just using that as an example) if you do not have some line of credit such as a personal or car loan, credit card, etc. A bank can not accurately gauge your credit if you have no credit history. Having decent income with no debt will only get you so far.