NVIDIA asked some retailers to sell to gamers first, but the company has no real power to enforce this. The demand from cryptocurrency miners is just too huge, and this gives distributors and large retailers a lot of power. The more demand for AMD and NVIDIA GPUs, the higher the prices.
So why isn't supply going up? The problem here is that demand from cryptocurrency miners could dry up overnight. This has happened before and is making everyone cautious. To dramatically increase video card production, GPU orders need to be placed a couple of months in advance.
As FUD Zilla points out, the risk here is that cryptocurrency mining demand dries up before these additional cards even hit the market. The result would be that AMD and/or NVIDIA would be stuck with hundreds of thousand of GPUs that can't be sold:
So in order to keep the channel happy, Nvidia or AMD would have to order, let's say 50 percent more chips today, probably even more, and risk being stuck with hundreds of thousands of chips if market demand plummets. It is the same gamble that crypto market is betting on every day - everyone who jumped into mining or selling the crypto currencies hopes that they will sell at a profit, and obviously higher than she or he bought them for. Unfortunately, not everyone can win, someone has to lose too.