I have come across the issue of EoL products being used several times whilst carrying out IT and Cyber Security Audits. Often the client has no idea that the firewall or internet connected printer they are relying on is no longer supported by the manufacturer. I have written about this issue before here.
here is a real world example where what appears to be perfectly functional equipment becomes a cyber security risk because it is no longer supported:
D-Link says it is not fixing four RCE flaws in DIR-846W routers – BleepingComputer
Clive Catton MSc (Cyber Security) – by-line and other articles