Enough features to distinguish on, enough political/managerial reasons for choosing an independent FLOSS engine over one controlled by Google.
Sure, Edge/MS won't move to this engine anywhere soon. Nor will Brave switch over tomorrow, or electron rebuild around their tooling. But the world is full or "HTML-2-PDF renderers, headless testing toolkits, (embedded) webview-libraries or electron-alike toolkits, which are now almost all exclusively Chromium based.
A lot of GUI based programs should think of implementing parts of it as a library others can use. I remember early Git implementations in IDEs where they just ran git commands in the background and parsed the command line output. Imagine if the same had been done with SQLite, would it still be as popular today?
I don't have much experience with creating desktop software, but it seems to me that separating the GUI from the "engine" would bring other benefits too.
I have often looked at OSS and wanted to use parts of it myself. An email client might have a really good mail parser that handles encoding, attachments etc. But decoupling it from the rest of the program would take too much time.