I don’t really understand your point. Just because all the implementations support the `asm` keyword doesn’t mean you need to know the assembly language of every CPU that has a c++ compiler.
You can write your code in modern c++ and ignore prehistoric carbuncles (some of which have been deprecated and eliminated FWIW). And you can call external code written in older dialects without having to look into its source code.
That's great for a greenfield project where you're the only developer. If it's multiple people, you have to deal with whatever subset the powers-that-be on your team wish to use. If it's not greenfield, you have to deal with the subset exists in the codebase.
And if you're a Dirty Harry type like me, debugging issues with dozens of disparate codebases written in various crap subsets, you pretty much have to know the whole cursed thing.
