Why are there so many good video game adaptations, but not good adaptations of video games

We had a discussion in our Monday meeting that got louder than things normally do, because The Last Of Us TV show came up, and we found ourselves divided into two camps. Well, three. Camp one was excited for the TV show and camp two posited that there's no point making an adaptation of something if your adaptation is just the same thing. (The third camp was "eh, I might check it out" and watched the other two camps duking it out). I was in camp two. If you're adapting something, adapt! Make changes! Otherwise I might as well just consume the original thing again! The Last Of Us has already been released, what, three times?

This was made funnier by the fact that nobody on staff had seen the TV show, so we were just arguing about tweets we'd seen that describe the show, the worst way to conduct a discussion outside of e.g. scrawling insults on the side of Teslas and self-driving them into each other's front doors. But it got me to thinking about adaptations, because there have been loads of adaptations of things that aren't games into video games. What goes wrong in the other direction?