It can't happen because the mnimum age for an ATPL is 21 !
Don't forget people that you need an ATPL up the front of an airliner!
You won't see an 18 year old at the controls of a QF or Rex aircraft any time soon!
It is my belief that time spent until you're in your early 20's should be gaining life experience in a charter or flying school capacity rather than sitting in the right seat of a small airliner because mummy and daddy paid for your Qantas cadetship!