Things can suddenly or progressively break after a while if a system gets too far behind regarding updates.

A few plausible examples:

• The navigation system can send you to non-existing road if it doesn't know about recent major roadworks. Or give you old/bad speed limit and cause you to get a ticket.
• The GPS receiver may fail to obtain a location if satellite orbit or other parameters shifted too much since the last update (happened to me once after several years).
• A bug may manifest itself only after a while or a given date (similar to y2k) and break some features.
• A vulnerability may be discovered, which make cars that aren't updated easy to steal as knowledge of the vulnerability spread
• ...