Depending on the particular scheme:

1. Penalties generally increase exponentially over time. Nothing like a EUR 50 ticket which is not EUR 750.
2. Some jurisdictions make the registered owner responsible. If that's a rental, the rental has your CC and you will see the charge + a hefty administrative fee, sooner or later (go back and read your rental contract for the amounts).
3. Some jurisdictions turn these over to collection. Depending on your residence, this can adversely affect credit.
4. Some just sit back and wait. There are those who can avoid visiting a country, but it's awfully hard to tell your employer that you can't travel to a place where you're needed because you are fearful of being hit up for some off the charts unpaid penalty.

This one's only EUR 69.