In descending order of significance (i.e. most important objective first):
1. ungoogled-chromium is Google Chromium, sans dependency on Google web services.
2. ungoogled-chromium retains the default Chromium experience as closely as possible.
Unlike other Chromium forks that have their own visions of a web browser, ungoogled-chromium is essentially a drop-in replacement for Chromium.
3. ungoogled-chromium features tweaks to enhance privacy, control, and transparency.
However, almost all of these features must be manually activated or enabled. For more details, see Feature Overview.
What's the point? It's open source. So some people naturally spend the effort to maintain something like https://github.com/ungoogled-software/ungoogled-chromium
> It's open source
Harder to distribute than unzip-and-run binaries.
ungoogled-chromium literally offers unzip-and-run binaries - it's what I use on a day-to-day basis.
There AppImages for Linux. Can't speak for the other OSs.