ASCII was supposed to be a standard for American Information Interchange (as pointed out above), hence the name. And being first it followed the now-increasingly-popular YAGNI rule.

Hey, I didn't notice that IBM (International Business Machines) fixed the problem with its highly vaunted and hopelessly idiotic EBCDIC, either.

When ASCII became problematic due to its limitations, it was extended (in the best style of Micros~1); now we have UNICODE, and a whole raft of ISO 8859's. And then there are the Asians: JIS, Shift-JIS, GB2232, GB18030, Big 5 et al. So now you can have your \ufffd in any one of several dozen encoding schemes. Ain't choice grand?