I found that have two main use cases:
1) Search - It is nice that Kagi search is less SEO spammed. That a big appeal. However, I don't reach for a search engine when I have a topical question anymore. I reach for something like o3 with search, so I don't need to dig through a bunch of articles. Over the last few years my pure search volume has dramatically reduced.
2) Maps - I travel a lot. When I toss a business into the search bar, 90% of the time I want to see it on a map. Google's Maps experience is just far superior to Kagi's. I find that I end up typing maps.google.com more often than I am happy Kagi ran the search.
I don't mind paying for a product; it just didn't work for me.
Side note: I personally dislike that their favicon looks like a "g" for google. It's always confused me.