Outside of Firefox, and very niche browsers, every other browser is built on Chromium. Edge, Opera, Chrome, etc. They all just add in their own customizations and things. You have to go look directly for Chromium, which the vast majority of the world doesn’t know exist. That’s the only reason why.
According to OSM, they’re complementary and they kind of work together:
https://blog.openstreetmap.org/2022/12/22/views-from-the-openstreetmap-foundation-on-the-launch-of-overture/