You've got some very confused beliefs about what mkv is and why it's used. Mkv is a container, not a codec, which is most often used to store lossy video and audio tracks. It can store lossless tracks too, but that is uncommon in practice. Other popular containers, such as mp4 (e.g. MPEG-4 Part 14), can also store lossless tracks.
The biggest reason anime people prefer mkv to mp4 is because mkv supports the ASS/SSA subtitle format, which is favored by the anime subbing community for its extremely versatile formatting options. For instance, it is common for subbers to cover up signs containing Japanese text with translated subtitle text, tracked to the video, styled and transformed to appear virtually seamless. Less relevant but still important to some people, mkv supports a plethera of old (and very lossy) video codecs, which is sometimes relevant when it comes to repackaging old encodes of hard to find media. Being able to copy in the old video codec without transcoding preserves what little quality there is while allowing you to package it with modern subtitles. Mkv also has superior support for chapters, metadata, etc.
But I get it, you hate anime and think weebs are pervs. I thought you were a man who values tolerance highly, but whatever man. It has little bearing on technical matters. Incidentally, anime people generally favor mpv above VLC, because the ASS/SSA support is a lot better in mpv (mpv uses it for rendering the psuedo-GUI.)
As for the bugs and UX issues in VLC, I assume that your claims are more accurate than your understanding of media containers, but VLC is nevertheless the best video player to recommend to nontechnical users you might find yourself playing tech support for. They won't tinker with it and therefore won't discover most of the issues you're talking about. What they'll get out of it is a media player that plays whatever file they throw at it, without feeling the need to run sketchy "codec packs" they found god knows where on the internet.
Those aren't my confused beliefs, I was literally quoting the text at the links.
And you don't have to be so defensive by jumping to conclusions that I hate "weebs" and think they're all pervs (although the ones obsessed with sexualizing little girls are certainly misogynistic pervs). What I hate is spending precious time and effort catering to small groups of people obsessed with particular fetishes (perverted and misogynistic or not), at the expense of prioritizing solving the real problems of large groups of people suffering from particular egregious bugs and usability issues.
Remember: it's been A DOZEN YEARS since I reported the problems in great detail with step-by-step instructions to reproduce them, and they STILL haven't fixed those problems that I and other people reported. Maybe refusing to ever acknowledge or fix those horrible bugs is Rémi Denis-Courmont's way of getting revenge on me for hurting his feelings by posting a wall of text he claims he didn't bother to read, at the expense of all of his other users and the quality and usability of VLC, so now I'm sorry I ever took the time to try to help by reporting and documenting the bug, and I'll never do that again, but he still seems pretty arrogant and thin skinned to me, even quite recently. And VLC's user interface STILL sucks.
Edit: The link I'm quoting is myself, quoting the text in another link written by SOMEONE ELSE. Literally, the VLC release notes, and an anime discussion about MKV which I read before I quoted it, so I already fully understand what you're mansplaining to me, and I'm not complaining about cartoon porn or MKV, I'm complaining about idiotic priorities. I'm sorry I touched a nerve that triggered you, but I don't hate "weebs" or porn, just misogyny and child abuse and terrible user interfaces. If you want to argue in favor of those things, go back to 4chan.
The link you're quoting is yourself, complaining about anime porn and asserting that mkv is popular because it's lossless.
Mkv really has nothing to do with VLCs usability problems. You're just grinding an axe against it because it's not a feature you value (or seem to even understand) but is valued by people you have evident disdain for (why even bring pornography into the discussion?)
The biggest reason anime people prefer mkv to mp4 is because mkv supports the ASS/SSA subtitle format, which is favored by the anime subbing community for its extremely versatile formatting options. For instance, it is common for subbers to cover up signs containing Japanese text with translated subtitle text, tracked to the video, styled and transformed to appear virtually seamless. Less relevant but still important to some people, mkv supports a plethera of old (and very lossy) video codecs, which is sometimes relevant when it comes to repackaging old encodes of hard to find media. Being able to copy in the old video codec without transcoding preserves what little quality there is while allowing you to package it with modern subtitles. Mkv also has superior support for chapters, metadata, etc.
But I get it, you hate anime and think weebs are pervs. I thought you were a man who values tolerance highly, but whatever man. It has little bearing on technical matters. Incidentally, anime people generally favor mpv above VLC, because the ASS/SSA support is a lot better in mpv (mpv uses it for rendering the psuedo-GUI.)
As for the bugs and UX issues in VLC, I assume that your claims are more accurate than your understanding of media containers, but VLC is nevertheless the best video player to recommend to nontechnical users you might find yourself playing tech support for. They won't tinker with it and therefore won't discover most of the issues you're talking about. What they'll get out of it is a media player that plays whatever file they throw at it, without feeling the need to run sketchy "codec packs" they found god knows where on the internet.