Stores like Newegg and Microcenter want to be selling video cards to DIY system builders rather than cryptominers (but will sell them to whoever wants to buy). Everyone is afraid that cryptominers is not a stable market, they will buy a lot of cards now, but they will be gone next year, that if these shortages last too long it will negatively effect their primary market of DIY builders. These companies worked hard to gain market share of that market and they are really afraid this will cost them an entire generation of DIY builders who are going to either move to console, decide they don't really need to upgrade that often, or (most worryingly) find other outlets to buy from.
The idea here is that the DIY market will not handle the huge markup on GPUs that the cryptomarket can obviously handle, but a large percentage of the DIY market often buys several parts at a time to do new builds, so if they can bundle popular parts together they can price for the DIY market while still charging a premium to the Cryptominer market.