Because they can’t help telling everyone how games should be made?
…Wait this wasn’t supposed to be a joke, was it?
I didn’t think that actually happened very often, but it doesn’t surprise me when it does. To be a good games journalist, you need to understand a lot about makes games and gamers tick. There’s a huge overlap in the skills needed to design a successful and fun game, and the other skills can be picked up easily enough, or hired out. At least, “easily enough” if you’re really motivated. It’s still a lot of time and effort, but it’s very rewarding, especially if you’ve got a good game idea.
When I watch Digital Foundry and they discuss the technical issues of a game, I can’t help but think they’d be great as a release manager/director or something for a big AAA game. Not only could they pick up on QA issues, but they’d know enough to say what the cause is and estimate how much work it would be to fix. And more importantly, they know what game reviewers are looking for, so they know what will impress them.
So yeah, it makes a ton of sense. They probably won’t be writing code or creating assets, but they’ll know when voice acting is good enough, which option to use to help fix performance issues in a given scene, etc. They could even help design games.
Because it’s the next step in exerting their demands for control?