In Holland it's much worse. You aren't allowed to use public transport unless you have minimal 20 EUR balance on your card (or agree to be tracked and I assume have your travel data sold / 'lost').
This applies for return journeys, so after the first leg of the journey you need to make sure there's 20 EUR left or you're screwed.
Other than the obvious money-grab by the authority (1 million cards x 20 EUR x 1% / 12 months == 16666 EUR income each month), what's the reasoning behind this? Only financially solvent individuals can use public transport?
Fair, per-kilometer pricing. Quoting from the english version of the page linked above[0]:
When you travel on credit, a boarding fare will be debited from your card when you
check in. When you check out, the boarding fare will be refunded and you will be
charged for the number of kilometres you travelled. If you do not check out, you
will pay the full boarding fare.
Not everything that looks like a blatant money grab is one. Hanlon's Razor[1] prevails once again.
I'm assuming they have variable pricing based on distance traveled, and 20 EUR covers the highest fare for the system. That could just be my optimistic bias speaking though.
This applies for return journeys, so after the first leg of the journey you need to make sure there's 20 EUR left or you're screwed.