Proof Of keys was meant as way for the Bitcoin community of retaking and exercising control of their bitcoins ( not your keys not your Coins) by simultaneously withdrawing all their Bitcoins every January 3rd of the year from centralized exchanges, third-party bitcoin services and Custodial wallet providers and moving it to private wallets controlled by themselves.
Why should people use non-custodial wallets to store all of their bitcoin?
Why should people prove their ownership on Jan 3rd each year and not on other days?
The activities can only help third party companies to have more proofs on how many bitcoin addresses are still active and they can run analysis on how many bitcoin potentially was lost (from UTXO data).
https://hodlwave.com/