One big reason that demand is low is that the current generation of GPUs are way too expensive, with top-end GPUs about twice what they used to cost a few years ago, very poor improvements in performance-per-$, and anythign below the top end offering even more dubious value for money especially on the AMD side. Originally those high prices were a result of high demand compared to supply, but the companies seem to have gotten greedy and decided they can permanently keep prices high and just throttle back supply to keep them there.