I would hope so too.
The issue is with some apps there's quite literally nothing one can see as being changed far as the app's operation/features are concerned, yet the app will get slower as the phone gets older.
If things are being updated (security/bug issues excluded) that do not make the app look better or add new features, yet makes the app require more resources, then why update?
Say there's an app that plays MP4 videos and 5 versions later it still plays the same MP4 videos (nothing has changed to the MP4 format at all during that time with no bug fixes or security patches) and the app is still the exact same as it was 5 versions ago, but it runs slower. Why does it run slower?
Is there's something I'm missing here?