Legacy
Ex-translator and layout designer here. I've had to get used to and work with about a dozen or more different keyboard layouts in that many or more languages, in a few different countries.
Here's my experience:
- the differences are simply legacy, and rarely have real practical justification (like $ vs £).
- almost everyone is nevertheless super-defensive about the layout they are used to.
- yet, anyone can get used to any new keyboard in a week or so (trust me, I've been through it a bunch of times).
- to top this off, most keyboards are full of silly, pointless designs. Often keys that are very frequently used are behind a modifier, while keys nobody uses have a super prominent position, even enlarged, like the friggin CAPS LOCK (my biggest pet peeve). That, if any, could just be a "both shifts at once" or option-shift or whatever.
I like the US Keyboard best (with some small customizations). Not because it's the one I'm most used to, but it's because the one I chose as my favorite after being used to about a dozen others when I stopped working in translation/layout. FWIW I'm not a native english speaker and live in a francophone country (yes, the HORRID azerty). The US keyboard has the least keys, and thus is the least cramped. All those rarely used symbols etc are perfectly easy to place behind modifiers and you just get used to it, and they do not slow you down in the least.
Non-US keyboards are (usually) the US plus they've just added buttons for their special keys like ä ö å ç etc instead of replacing keys. So they are typically more cramped. What's worse, they often have totally idiotic keys that maybe 0.1% of anyone uses yet are prominently featured (not one of my UK colleagues can explain to me what the second pipe symbol (unbroken vs broken) is for, or the Not sign (¬).
The Mac compact variant of UK keyboard is a noticeable improvement over the standard PC keyboard, and is only down to two sillinesses (the top left key under esc, anyone really use that? and the caps lock, of course).
In short, all keyboards have a pile of modifiers: shift/ctrl/alt/apple/fn/option and sometimes the left vs right are different (like alt vs altgr). Ideally I like all the most common keys available and shove the rest behind modifiers. Modifying a keyboard to your personal preference is easy enough, anyway.
Is it a problem? No of course not really, not normally... but on a 12" or smaller laptop it can really bug the crap out of you, because most manufacturers seem adamant to keep all those nigh-useless keys on board, coming up with cramped monstrosities.
Everyone loves to copy Apple on all their designs EXCEPT this one, lol....
Rant over...