

The why is easy. As others said, the vast majority of error messages are entirely useless for you, the user, because there’s not a single thing you can possibly do to address it. What are you gonna do about a database connection issue, or bad cache, or broken Javascript? Nothing. So don’t worry about it. Besides people are less panicky when they see an oops rather than a stack trace or a cryptic error message.
And don’t worry, people who know how to write up useful support tickets and bug reports know how to do it even when all they can see is an “oops”. Builtin browser dev tools will have information they can use to help the devs.
Widewine? Maybe they have some content that requires L1, which still doesn’t work on Linux because of totally legitimate technical reasons that are absolutely not at all utter horseshit. Or they might be using some browser APIs that are not properly supported on Linux. There are a few of those.