Right but there were many other good mapping apps at the time Apple introduced their maps app, and since then there has also been the Google-developed Google Maps app — all these are updated individually.
Aside from Maps (for which there were alternatives) the other apps haven't really had any urgent patches bundled into minor OS upgrades that I can recall.
I was cherry-picking Maps, but I remember that not all iOS apps were updated to the iOS7 look and feel when it came out, it was only at point releases that the few that weren't updated received the update. If Apple has a new shiny Safari browser ready, they have to bundle it with the whole OS update instead of pushing an update on the App Store.
One could even say that the advantage of Google being able to system app updates on the Play Store is that Android apps competing with iOS ones (not a great comparison, but Google Now and Siri) have an advantage in that Google keeps on pushing updates regularly as and when they are ready, whereas Apple would update Siri during a major OS update or the incremental ones. [I am aware that back-end services/responses are updated regularly by both, but I'm referring to code which would change an app's behaviour].
> I was cherry-picking Maps, but I remember that not all iOS apps were updated to the iOS7 look and feel when it came out
This is not true for apps that come with the OS. Some Apple apps were updated later, but only those that come from the App Store like any other regular 3rd party app.
The advantage Google has to be able to update core apps from the store instead of through OS updates is specific to Android's nature, because it allows them to work around OS updates not being available to customers (because of carriers, OEMs, whatever). Apple doesn't have that problem because they update the OS themselves. Also, Google likes to update its software more often than Apple does.
Aside from Maps (for which there were alternatives) the other apps haven't really had any urgent patches bundled into minor OS upgrades that I can recall.