I am just such a user that would not want to use a search engine whose searches could technically be tied to my account and my identity. However much Kagi (or any other company) assures me that my data is private or is not being tied to my identity, it still requires me to put my trust in them, and some users such as myself are not willing to do that for something as sensitive as search engine queries.
However, with the sort of blind signature / zero-knowledge proof method that Privacy Pass uses, trust is not required. The system works by making it impossible to associate someone's payment information with their account. It would work something like this:
1) A user uses your payment system to make a payment, but without specifying their Kagi account
2) You get a notification that the payment was successful, and sign a special a token for the user without actually knowing what the token is
3) The user uses the signed token on their Kagi account to prove they paid for it, but due to the nature of the token, it's not possible to link it back to their payment
Voilà, their account is now able to be anonymous without requiring trust. (Though it would still be up to the user to use an anonymous email address, or even mask their IP address using something like a proxy or VPN.)
I think there's a lot of privacy conscious people out there who would appreciate companies like Kagi providing a method that guarantees that their data (in this case searches) are truly private. I won't speak to how many there are, but I'm at least one of them. And I think there's a lot of symbolic significance to implementing such a system, because it would demonstrate how committed you are to user privacy.
