AMD and Intel have much more important things to do with their time and resources. AMD didn't even give a shit when their GPUs were all-the-rage during the GPU mining days.
But they are among the most establised, biggest shovel makers... They've only made dirt rakes and trowels, though?
I'll continue with that analogy, lol. They make all kinds of tools for big mining operations; pickaxes, backhoes, piledrivers, excavators, etc. But I imagine that BTC mining is such a rare yet valueless mineral (by their standards) that there isn't enough money in developing, marketing and selling tools for it. They would rather sell tools at high volume with high margins. And bitcoin mining just isn't lucrative enough.
It's just by chance that their CPUs and GPUs were once valuable mining tools. But they probably barely noticed any improvement to their bottom line from the sale of those tools.