That's an arbitrary style choice in the spec. Saying "it's void so never use / " is no more natural than saying "it's void so always use /". Arguably, it's bad

That's an arbitrary style choice in the spec. Saying "it's void so never use / " is no more natural than saying "it's void so always use /". Arguably, it's bad style to use the same syntax for opening a tag as for a void tag, because it forces semantics into the syntax for trivial benefit. With out the "/", your HTML syntax parser now has to include a lexicon of all the void tags, and be updated with spec revisions.