They provide the parsing engine with better clues for the AST that is given to the JavaDoc agent (aka doclet), which allows to customize the document generation process.
That crap allows for tooling that Go will never have thanks community culture.
Keep building strawmen, I'll be building software.
“That crap” is at least in part a reaction to the endless stream of DocTagFactoryFactoryFactories patterns that came out of the Java world. While I think Java is a decent language with a good ecosystem, I’m completely over the idea that the only way to do things is the Java Enterprise(tm) way.