You might not care too much, and it clearly depends on the application, but for me updating a software that doesn't use anymore a library for getting user input that leads to a buffer overflow if you insert a certain character, or similar things (like remote code execution, etc.), can be quite important. Finally, apps are most of the time connected to the Internet, which makes them inherently vulnerable.

After searching "android software libraries CVEs" I found this in the first results' page: https://github.com/dotanuki-labs/android-oss-cves-research

It might be outdated, but the principle still applies.

It's very unlikely that your application is self-sufficient and doesn't need updates.

EDIT: I read the message from Apple as a "hopeful" attempt to say "come on, man at least update the dependencies".