Impervious to reason? Yes. This thread is full of reasons, and you've ignored them all. Not even attempting to counter argue, just ignored them. You're like a child: I want! I want!

Requirement? Yes. An industry standard term, that you obviously have no knowledge of, which explains a lot.

What reason has anyone given to the question of why a hex constant (e.g. 0xa0) shouldn't be able It is not that it could not be done, it is that there is no good reason to do it.

And the potential for silent failures, where a non-number that would now look like a hex or octal number, is accidentally used in a numeric context, that would currently warn loudly, is too high a price to pay for something you think would be nice to have even if nobody needs it or would use it.