The thing is this isn’t a single spectrum. The requirement the AGPL adds to the GPL could be applied to the LGPL without including the requirements added by the GPL.
To take the video game analogy, it’s more like asking why you can’t set the brightness above 50% if the graphics quality is set to ultra.
The answer here is that the FSF likely doesn’t see the utility in such a license.




And, critically distinct from the AGPL, they wouldn’t have to open source their full service — just the changes to the library.