Eighty percent of youths are employed. Of the one fifth who are not, it's likely that many of them are able to rely upon their parents or older, employed siblings for support while they themselves are seeking employment.
Weaken employee protections and social responsibility provisions and large numbers of the older, higher-paid workers will likely be replaced by lower-paid younger workers. Neither the still-employed non-youths nor the newly-employed youths nor the eighty percent of youths who had jobs will have any job security anymore.
That doesn't sound like a societal win at all.
The people pushing the youth unemployment figure don't actually care about youth unemployment. The point is to beat everyone over the head with that figure to get them to agree to stripping everyone's worker protections away.