If Kagi were as popular as Google, you'd quickly see pages appear "without ads", that looks suspiciously like what an ad would say. The problem is SEO, and it affects the mainstream search engine because that's what's worth optimising for.
For instance, Google product search results would likely be greatly improved by always showing relevant reddit posts first. But this would last a very short amount of time until reddit would be completely drowned in junk. (I've seen people argue that this is already the case, but searching reddit still tends to work well for the products I search for)
We can be happy that Google search hasn't gone this way, and as a Kagi user you should be glad that it's not a more popular engine, as the quality of results likely highly depend on that just fact.
In a way the ads-filled product search results are better, because at least they're honestly trying to sell you the product you are searching for rather than making fake comparison sites pretending to be genuine content.