People who use GPLv3 want the code to stay open/libre under any circumstances. If this is the goal, why not use the AGPL instead, even for applications which are not served over a network?
This takes away the possibility that people integrate parts of your program into a proprietary network application, even if this seems improbable. There’s nothing to loose with using this license, but potentially some gain.
Only reason I can think of is that AGPL is less known and trusted which may harm adoption.
Some time ago a client of me was looking for a solution to add watermarks to PDF files from their local on premise ERP system. The ERP system itself is a standard software. Obviously, they have a license to use that ERP but they definitely do not own the source code of it. Thus, they cannot change the license to AGPL or integrate it somehow.
I thought about writing a little plugin with Java in iFile to do that which is published unser AGPL. Using something under AGPL would mean that we have to make the entire solution available under that license.
Question 1: What is the entire solution in that scenario?
Question 2: AGPL says users must have access to the source code of the solution no matter if they use it locally, over network etc. But Who is the user in such a scenario?
Question 3: My client is not a software company, so they never published ANY source code or software. Where would you publish the code?
There is a lot of uncertainty when using AGPL software in a business context which will - in many cases - lead to the decision not to use the software at all.