You gotta make the GPUs to be competitive. I think it's a matter of unwilling as well.
Both nVidia and AMD sells pretty much every GPU they make. And Intel, I imagine does, as well.
AMD is obviously content where it is - they have limited fab allocation that they purchase - fab production is a limited asset for everyone. They choose to allocate that production time to their entire lineup - CPUs, APUs, Custom Market SOCs, GPUs, etc. So they could make more GPUs, they could attack market share. It's a long way to the top, but it isn't impossible over time with aggressive marketing and strategy. But why would you turn a current high margin product into a low margin high volume item that eats into the allocation of your more profitable segments? What sense does that make?
If i were a betting man - I would bet that AMD produces and sells just enough GPUs to offset the R&D for that. And uses that R&D in their other product lines (GCN in PS5, Vega forever in APUs, whatever they are doing with AI now) -- so it basically is free R&D/tech for their other product lines. I wouldn't be surprised at nVidia doing it much the same way. And in that manner, the GPU market is artificially supply constrained - both sides are only making enough to offset R&D, and then using that R&D in other, more profitable market lines. Which is brilliant, if you are thinking of it as an investor. It's soul-crushing if you think of it as a consumer.
I hate the position, because it means less actual competition. You could almost say it's market fixing, but I won't go quite that far. AMD is just happy to get nVidia-like margins on what they are currently producing and doesn't see the need to get into a bloody price war over it.
For both nVidia and AMD (and Intel, not that it's quite a three-horse race yet), neither company has GPUs as the core of their market any longer. For AMD it never was, they just happened to pounce on buying ATI when they saw an opportunity to get into the market, but it was never the dominant part of AMD's revenue. We, as gaming enthusiasts, just wish it were. nVidia is happy to have this position, as they primarily use it to pump their stock prices, but consumer sales aren't driving anything over there any longer - it was just
6% of nVidia's total revenue.