Really?
- Uninstalling a driver is something you shouldn't trigger. When a driver is introduced to the system, it usually stays there. This goes for all drivers I know of.
- The local app data stays there, we assume that >99% do want to keep their settings when uninstalling and installing again a later version etc.
- The registry settings comprise of about 1k of data, the same thing applies to that (settings usually want to be kept)
I disagree with each of your statements.
1. The OP is correct. There are many reasons that a user may choose to uninstall a driver. It might later be discovered it doesn't interact well with other drivers, it might be replaced by another vendor's driver, etc. Uninstall should get rid of it. Perhaps a reboot may be required, but it should be gone after uninstall. Every software manufacturer knows this.
2. Your assumption is way off, and regardless of the percentage of people who want to keep their data, the rest want it gone. A good uninstaller should give a user the option to keep or remove it.
3. Uninstallers should clean up their registry entries. Some use the registry to determine whether their product has ever been installed, but it's best practice for the uninstaller to remove whatever has been created by the app.
[EDIT: I noticed the registry key mentioned by the OP is "HKCU\Software\Kemper Amps". This is not the RigManager subkey. This is manufacturer key, which might be used for other products, so this key may be left in case other products are installed]