Why not use space-hyphen-space instead of the em dash?

Question

This is something I have wondered about for a while, and although it's the sort of thing we're conditioned to accept unquestioningly, I finally have to question it. This may come across as a bit rant-ish, but I feel it's based on valid concerns.

Why are em dashes (this—that) used instead of space-hyphen-space (this - that)?

Just to get a few points out of the way first - by "em dash", I am referring precisely to this character. And yes, I am familiar with the ways in which the em dash is used - I just can't bring myself to like it. Its similarity to the hyphen is irritating. And while the en dash is worse, depending on the typeface, it can easily cause an awkward pause of confusion.

The following sentence is what triggered me to ask this question:

Yet the challenges facing the nation and the world—climate change, inequality, the erosion of democracy—require innovations beyond weapons of war.

^Reference

The challenges facing the world-climate... change? No! Once we've made it to "democracy-require", we realize with certainty that we have parsed the punctuation incorrectly. We backtrack, re-read as an em dash, and the meaning becomes clear. But what a waste of time, and what unnecessary cognitive load! Now, some of you reading this are probably thinking: "It is obvious to me that the character in question is an em dash." And that's fine, because in the font this Stack Exchange site currently uses for the body of its questions, it's actually pretty clear, in my opinion. I would agree. However, let's try it out in a fixed-width font (Courier New) in Dark Mode:

It's now significantly less obvious.

Let's compare a few common dashes in this typeface:

^{HTML codes included for clarity}

The similarity of the en dash to the hyphen-minus is particularly hellish, but even the em dash is close enough to be a readability concern. And one can't help but wonder - if the purpose of the hyphen is to draw two ideas together, while the purpose of the em dash is to push them apart as a delimiter - then why were they made to look so darn similar?!

Now, for all practical purposes in daily life, I use space-hyphen-space instead of the em dash. But what's the worst that could happen if I were to use my convention in a publication? Would I incur all sorts of critical backlash from people accusing me of breaking the English language? Would I be "cancelled"? :-) Or would readers be pleased to find themselves parsing some sentences more easily, possibly without consciously knowing why?

Somebody please explain why em dashes have become a convention, and why some more legible alternative has not replaced it as of yet. And then, how "bad" would it be to take initiative and change this convention?

Answer 1

Merriam Webster

Spacing around an em dash varies. Most newspapers insert a space before and after the dash, and many popular magazines do the same, but most books and journals omit spacing, closing whatever comes before and after the em dash right up next to it. This website prefers the latter, its style requiring the closely held em dash in running text.

Merriam Webster is relaxed about a space round the em dash, although preferring no space. I take the opposite view. To have no space creates the impression that the words either side are linked, whereas the function of the dash is actually to associate or contrast the notions on either side. It is not reasonable to expect the average reader to be familiar with all the niceties of convention that distinguish the spaced hyphen, the spaced em dash, the unspaced hyphen (which creates a hyphenated word) and the unspaced em dash (which does not). Coming after meaning and grammar, these are less important matters of style.

For easy readability, the presence of two em dashes in a sentence creates a parenthetically defined thought that may — or may not — be removed without destroying the main vein of thought in the sentence.

Alternatively, one em dash followed by text ending in a stop of some sort introduces a thought that complements the previous — but is still removable without destroying the line of thought.

What to do? When editing, I assume my readers to be more concerned with the subject matter and grammar than with these conventions, so I reserve the unspaced hyphen for the hyphenated words, and the spaced em dash for the parenthetic thoughts.