Trying to be fair here - it's technically not linked to any blockchains. It's just (ab)using the cryptographic primitives provided by the Metamask wallet app to sign things with a key stored in the wallet. That key might (probably) also be used to sign things that end up on any sort of blockchain, e.g. ETH.
The reason to do this is some people do indeed have Metamask (a browser extension, yuck) already installed and a wallet set up - so technically this might be an easy way to enable signing for them.
The reasons not to do this, I already detailed above. It is a neat hack, that would fare tragically when applied to the masses.
No, the users are on Wikipedia. WMF has their own auth infrastructure already in place. It seems like the author of this "mockup" is proposing that WMF shitcan their entire user/auth infrastructure and replace it with a blonkchain-based one (and to be specific, this one particular ETH-based blonkchain.)
And then, of course, you'd apparently need to convince every Wikipedia user to get on the ETH PKI for this purpose? That does not seem like a rational choice.
Nothing about this mockup seems rational. It is entirely fake and frivolous. There's not even an explanation of the supposed benefits of this "endorsement" feature. Because it doesn't have any.
If there were 10M monthly real users, large crypto airdrops would go out to way more people. But even the big ones like Arbitrum and Optimism went out to like 500k “wallets”. Many of these were multiple wallets owned by the same people.
Daily transaction data on Etherscan shows that the most popular tokens like USDT/C are traded at most by under 100k wallets. OpenSea has like a few thousand wallets trading daily at most.
Real onchain users are not more than 1M a month, and that’s a stretch. I would put it closer to 500k real users, many of whom might have multiple addresses (I have 8).
And Facebook probably has a couple orders of magnitudes more, but you don't see anyone lining up to make a Facebook app for this.
Besides, Wikipedia already has user accounts. They even have a system for users with the appropriate permissions to approve revisions of a page -- no external crypto-nonsense needed.
The reason to do this is some people do indeed have Metamask (a browser extension, yuck) already installed and a wallet set up - so technically this might be an easy way to enable signing for them.
The reasons not to do this, I already detailed above. It is a neat hack, that would fare tragically when applied to the masses.