Because one likes the features available only in Chrome? I haven’t check recently and don’t know if this is still accurate, but Chromium used to not have the PDF reader and DRM support (for Netflix, etc.)
There are a number of foss and proprietary pdf readers for chromium/chrome. There are also netflix apps outside of chrome. You don't have to use Chrome...
Yes, pretty much, except that Canonical is nice enough to open source their patches. And they layer a ton of patches on top of the official kernel trees, mostly backports but also some new features. Their linux_5.0.0-36.39.diff is close to 35MB.
Yes, it's pretty easy to disassemble it and find out. It's basically auto-updates, some closed-source extensions like Chromecast (although you can manually download the Chromecast bits for Chromium if you'd like), some branding differences as compile-time #defines. https://chromium.googlesource.com/chromium/src/+/master/docs...
(Do you know that all of Chromium is in fact open source? Have you looked at the source and the build process? Are there any parts in it that are actually precompiled binary blobs?)
Netflix will play a 720p version if you don't have a DRM supported browser. Also netflix distributes native apps to all platforms, which means you don't need chrome to use netflix in full fidelity on any device except maybe linux?
