Treasure: Well, this is probably an unpopular opinion that I'll say right here, but I don't really see what's the problem with including that Widevine DRM by default.
One obvious issue: It's not open source. This means it can't be included in many Linux distributions (for example, Debian and Fedora).
That also leads to another issue: It can't (easily) be audited for security issues. If there is such an issue, then simply having it installed and viewing a web page could result in your computer being hacked.
There's also the fact that some people, me included, consider DRM to be unethical in the first place.