Steam has already disallowed "Applications built on blockchain technology that issue or allow exchange of cryptocurrencies or NFTs." from their platform. They have a very successful item marketplace which they get a cut of and aren't interested in blockchain systems competing. Epic has said they will allow it, presumably to differentiate themselves and because they don't have such a system.
https://www.theverge.com/2021/10/15/22728425/valve-steam-blo...