The main reason why

children would make substandard adults: they are real eedjits.

They fail to assimilate concepts as basic as the Monday morning blues.
Tsk, I ask you.

Cram them into a carriage packed to the roof with hot, angry, miserable and volatile commuters. Tell them that daddy will soon be paying between 15% and 20% more for the privilege.

Do they care?
Do they show any signs of distress?

Do they my fluffy arse...

They find fun applications for the condensation on the windows and have a laugh instead.

They may think that they hold the world in the palm of their hands, if not the world, at least the Custom House, well I have other news for them.
As long as they remain such jolly eedjits, drawing zombies in the condensation of a packed Dart carriage, my job as a grumpy copier and paster is safe.
I've got a PhD in Monday Morning Malaise.