I don’t have a source but this is based on my membership in the Kagi Discord server. Kagi search has decided to allow people to opt out of Brave results being included in the results and may asking Brave for free API access so that they aren’t being supported. I’m still unsure about whether I’ll resubscribe to Kagi. I might give Startpage a run for a bit.
I’m pretty sure it would require some major rewriting to make it opt-in. Plus they probably want the better experience for the majority of people who don’t care. I wouldn’t be so quick to draw conclusions