For games generally those parts can be shifted to the GPU because they feed the rendering pipeline anyway. Doing so has other benefits of lowering latency for that data to be picked up by the graphics bits already there etc. Also the clock speed penalty for AVX512 is pretty steep so unless you're going to do a lot of AVX512 it really doesn't make sense either. Games generally aren't using double precision either which is the AVX512 bread and butter. To make it more fun even if they were... a 4x4 matrix is composed of 256bit elements so the vast majority of register usage wouldn't be 512 bit anyway. The main benefit would be the new instructions more than the register width.

Long story short: Games generally aren't doing enough AVX to really benefit from it as implemented. They can be quite bursty in their use. Not to mention that Not every CPU even has AVX (because apparently Pentium Gold is a thing) even today.

If Intel convinced AMD to pick up the 256 bit versions and removed the clock speed penalties I could see them getting more use. But at the moment it's really just a feature for the HFT market primarily and even they are extremely careful in use because of the clock speed penalty. To the point they will literally benchmark both ways to make sure the penalty is overcome by the throughput.