What idiot came up with that, or is there legitimate reason?
And arguably, for the average user, it's still the right choice. It's only IT nerds who really need all those weird extra characters that aren't even real punctuation, and they can just switch over to the US layout.
When writing French on typewriters, people in Québec and the rest of Canada used a slightly modified US-keyboard layout that assigned the necessary accents and moved the symbols those keys used elsewhere. You could even use this layout with the US 104-keys keyboards on computers without losing much. Aside from having glyphs on your keys that didn't connect to what you were typing but people lived with it.
But when we moved to computers there came an opportunity to improve the keyboard. We could now assign keys to common letters with their accents together without losing anything, since we didn't need to focus on the additive nature of accents. You know, moving from a mechanical system to pure software.
So who jumped on the opportunity? The government of Québec led the charge in the early 90s for this new keyboard layout to replace the old French (Canada) layout. Feeling at some point that there was a risk of furthering divide in Canada, the federal government asked for some slight changes to the Québec proposal, in exchange for the promise of adopting it as the standard Canada-wide. Québec agreed, but Canada never did anything of value to help with adoption. So we're stuck with two standards, basically on the line of your OS: if you're on Windows, you're probably using the old French (Canada), and Mac users switched over to the new standard.
Every. single. keyboard layout. has a story surrounding its creation and its usage.
Programming languages used to be more cognizant of this. For example Pascal used mostly keywords rather than ASCII symbols, and this was entirely intentional to enable programmers in all countries to easily work in the language.
Of course C inherited Unix’s approach, killed Pascal, and nobody cares anymore. Except all those millions of non-English users trying to learn programming, but nobody in Silicon Valley thinks about them.
Still in the 1990s, Microsoft had a focus on BASIC which had a keyword-centric syntax. But Java and the web killed that.