How come Pat Cummins never played for Aus under 19s?

His rise has truly been meteoric. Considering how structured the Aus system is, it's strange that he doesn't seem to have represented Aus at under 17 or under 19 level.

He's still eligible.

It is to be noted that Patrick Cummins from NSW has not been included in this initial Australia Under-19 squad after consultation with the National Selection Panel and Cricket New South Wales on an appropriate plan to manage his commitments.
“There is still a long period before the World Cup and as Patrick has had an excellent break-through season for New South Wales, the YSP has had the opportunity to have a good look at him and what he is capable of so we have taken the option to give another young bowler this opportunity,” Chappell said.

This Cummins lad, is he any good?

Not at the moment.

Crocked.

Fark you, Trev. That's the end of that.

Probably for the best.