One of the extremely stupid reasons kagi needs to develop a browser is because ios safari prevents setting kagi as the default search engine, so they have to do some terrible hacks to get it to kind of work.
But with the Kagi extension all my searches are always redirected to Kagi on both Safari on iOS and Safari on macOS so I don't really see this as a real blocker as a user.
I understand that this is an onboarding problem, but for a technical user that's really not something preventing me from using Kagi (Like the other comment mentions).
That means the address bar is my main interaction with the browser.
The included ad-blocker being a big factor in the great UX.