Not all NFTs need to be bought or sold. They can just as easily be used as membership tokens that are given away.
Also, according to the website, only some of the communities will be locked behind NFTs. Others appear to be free to join just with an Ethereum account used as auth.
I haven't used the service so I'm not going to defend it but it makes sense for web3 communities to base their auth around the tech they're already using, and that is crypto wallets. Everyone in the community already has crypto wallets so the friction to join is very low.