There's an explicit company policy about game development that is separate from their open source policy. It, among other things, prevents you from working on a game project with anyone else.
I always thought that they were doing it because they had a really low opinion of their own game studio. Maybe they were trying to kill as much future competition as they were able to (legally).
Their first (and only) title they seem to be pushing hard to the public (in my opinion, at least. The Grand Tour Game wasn't really marketed): https://www.newworld.com/en-us
Games development are limitless in scope and technical complexity and very passion driven. So, a developer could spend countless hours each night improving his game.
Next day, all the team has is a tired developer, drinking coffee and unable to code straight or analyse issues without missing subtleties.
Opening a wordpress for your mom and her gardening hobby is a significantly less time consuming task.
In the early days of Amazon, Bezos rejected bus passes for employees stating bus passes encourage people to leave work to a a timetable and he would prefer them to be at office and leave only when they can.
Search inside for the 'Game Development Policy', it's separate from the intellectual property commitment. Reasoning is likely from Amazon Games Studios? I think there may be a concern that someone at Amazon might make the next flappy bird or Minecraft and Amazon couldn't capitalize on it.
This is the only rationale I can come up with for the game development policy: AGS hasn't produced anything in 8 years and what they have in the pipeline looks disappointing so...cross your fingers and hope one of your employees makes the next Minecraft.
Heh. I worked in Amazon Games for a bit. It was a very common question. Along with, "What games have they made?" (Breakaway a 'sports brawler', The Grand Tour game a tie in for the show, New World an mmo about being a colonizer, Crucible a third person shooter.)