1) To make the business viable and profitable. I searched a bit more and saw a post where the founder said they do expect to be profitable with 50,000 users. That still seems a tight budget if people are paying $10/20 amounts. Also I believe Kagi use google results currently so there has to be a big risk google limit what they can do if they ever become a threat of a business or generally remain beholdent to their main competitors via access and pricing rather than have independent infrastructure.

2) I would love to see a real challenger to Google. A paid model will not likely be that.

I completely understand the responses and there is also value in staying ad free, but there is also value in doing ads a better way rather than all or nothing and hopefully not going down the supply slope type arguments by setting clear and transparent rules at the beginning so that tension doesn't exist or is limited.