Don't understand why I'm not seeing the one you say should be there.
Sorry, I haven't a clue. I've never heard of anyone having a problem before now.
I was able to install 14.7 from the apple icon / system settings. That said, what is the point of the installassistant package installation?
Suppose you want an installer for 14.6.1 now that 14.7 has been released - it won't be available in the App Store. The same goes for OS versions which aren't compatible with the hardware you want to use to do the download (you
can download dmg files for a few much older OS versions though, even on incompatible hardware).
If you're running macOS Monterey or higher,
the Mist app can be a convenient way of creating installers. In addition to installer apps, it can also create installer USBs and ISOs.