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.
GNU licenses aren’t about denying people from making money, they’re about ensuring that they share their code changes with everyone. AGPL was created to solve a new edge case concerning SaaS companies like AWS, Azure, Google, Alibaba, etc.