How odd! But I believe you are right [1], all two dozen Apple keyboards have the option (aka "alt") key, including the "British" one, but not the "English" one... (Who's the imperialist now ;-)) Perhaps the idea is that the average user only needs the option key for non-ascii characters like £, so Americans won't need it.
Oh wow! I stand corrected, mostly. I was not aware that was an American thing. How very strange.
It's in flux. International English keyboards (a bit different layout from US and not the UK one either) used to have the symbols. The most recent iteration has the command symbol, but not the others, it says "control" and "alt option" on them. Still has a symbol on the return, delete and tab keys instead of US-style labels.
Only on American keyboards, apparently.