You can just make a parser that ignores comments, while still allowing them in the syntax. You don't need to store the comments in the AST, or to actually parse them. You just need to skip them.
That only works if you control the data that gets parsed.
Imagine you’re a HTML parser library author in 1998. You’ve been happily skipping comments. Now you get complaints that your parser doesn’t see JavaScript. Turns out that everyone has agreed that these new script tags should be embedded inside comments.
Should you keep skipping comments and tell your users you’ll never support this HTML that everybody else now considers valid?
You can just make a parser that ignores comments, while still allowing them in the syntax. You don't need to store the comments in the AST, or to actually parse them. You just need to skip them.