I would honestly like an answer from someone.
If I had a 100,000 line of code video game that took me years to make, and I want to use some 10x10 pixel piece of GPLed art that took someone a few minutes to make, does that mean I have to release my 100,000 lines of code open source? I think it does and people have suggested it to me in the past.
This is why I think artists get lulled into thinking they can license under GPL and people can use their art as long as they put their name in the credits, but that isn't the result at all. Artists who want their art to be used freely in video games probably want to use Creative Commons license, and not CC-BY.