Agree on under-reported. But what externalities?

Addiction. Misappropriation of others' secrets. Perverse incentives.

As a German train driver this excites me greatly.

Having a gambling addict in your life can be just as destructive if not more destructive as having a drug addict in your life.

This is something that most people don't currently understand because most people don't really have much experience with gambling addicts and the sort of horrible things they will do to satisfy their cravings, but as the amount of gamblers in society grows explosively, we're all going to be feeling the effects of being surrounded by these people.

There are (illegal) ways to delay trains as a person

Should be noted that this is just a meme, nothing with real money. Its a joke based on the constant delay of DB trains

More gambling addicts in gutters.