Bink isn't the codec, though that's good too, it's the software stack. How do you render AV1 on a PS4 or a Nintendo Switch, synchronize it with the audio stream? No, seriously, tell me.
GStreamer with its ridiculous threading architecture and lock-heavy approach? You think that's going to run on a console CPU? ffmpeg / libavcodec? Yes, we can hook that up, have it crank out YUV buffers and display those on the GPU, or we can just use Bink. Yes, it costs a ton of money, but based on when I evaluated it last, it was almost twice as fast as libvpx on our target platforms, it was well-suited for games (worked well with custom allocation strategies, didn't start a bunch of threads by itself, integrated well into our renderer), was easy to integrate, the toolchain was lovely, and when we needed help with a bug, we got an email back the same day from Jeff. RAD's support is top-notch.
Multimedia is not too big of a problem that a company like Epic can probably spend a few days integrating libvpx and opus to make a custom video solution, but big enough that most smaller studios with custom engines don't have time to spend on that, and those are the sort of problems that RAD likes to tackle.