This is real reason.
Nvidia been thro this once already.
Some one else mentioned, they want to mine to recoup cost for gpu, Well if gpu is no good for mining demand will go back to normal and price will drop.
In the end this is good.
If miners stop buying GPUs, demand will drop.
Back to normal is totally different thing.
What people here and elsewhere seem to be ignoring, is that demand from just gamers is crazy.
The Steam survey pointed to an estimated 3.5 million GeForce 3000 series cards being in the hands of gamers (some of whom may mine, but a miner with 10s, 100s, or 1,000s of cards would not install Steam).
Sony have sold close to 8 million PS5.
Microsoft less, but still many millions.
Gaming (yes, sorry GPCGMR but console buyers are gamers too) demand is simply crazy.
Can't find any estimates of how many GeForce series 3000 cards are in the hands of miners, but even if it were a million I am not sure it's enough to change things quickly as I think PC gamers could easily have bought 4.5 million and still have a shortage.
As for Nvidia's motives: product segmentation is a favourite of theirs so forcing miners to buy mining-only cards is good for Nvidia. The fact the miners can't sell them later to games is also good for Nvidia less so for gamers (as buyers, although a glut of used cards wouldn't help those who want to upgrade and sell their old cards). In the meantime, the demand from both gamers and miners hasn't done Nvidia any harm, and keeps them from having to reduce official prices or even the price they sell to OEMs to give the OEMs a chance to actually release something closer to the mostly fictional RRP.
As for the Nvidia PR spin of being the gamer's friend: pull the other one!