How is it more convenient to add lines under a title than start with a # ? How is it better to limit to h1 and h2 only?

I sort of lament the use of lines under headings, as they look visually better for human readers of Markdown, but they're worse in other ways: ambiguous heading levels (quick, which is h2, `===` or `---`?), and less token-efficient.

For me, the use of indentation over ``` for code blocks is a complete non-starter, though. It's hostile to copy-and-paste.