And for a long time MediaWiki didn't have a proper parser for that markup, just a bunch of regexes that would transform it into HTML. I don't know if they have

And for a long time MediaWiki didn't have a proper parser for that markup, just a bunch of regexes that would transform it into HTML. I don't know if they have a proper parser now, but for reasons of backwards compatibility it must be lenient/forgiving, which means that converting all of Wikipedia to markdown is basically impossible now. So MediaWiki markup will stay with us for as long as there are MediaWiki wikis.