C was developed on a PDP-11 that had 64Kb of memory. That's not much of any at all. Therefore, the compiler must be extremely tightly coded.
The fundamental rules of the C language are pretty simple. But articles like these expose consequences of such simple rules. Fixing them requires adding more code. Adding more code means less room for the code being compiled.
Therefore, if the intended use of the language works, the pragmatic approach would be to simply not worry about the quirky consequences.
A more interesting question would be "why do these characteristics persist in modern C compilers?"
The stock answer is "backwards compatibility", "Obfuscated C Code contests" and "gotcha job interview questions". My argument would be that there is no reason for the persistence of such "junk DNA" and it should be deprecated and removed.
I've done my part. D doesn't support that stuff, even though the basic use of the language is easily confused with C.
For example:
#include <stdio.h>
void main()
{
int i;
for (i = 0; i < 10; ++i);
printf("%d\n", i);
}
The equivalent D code:
import core.stdc.stdio;
void main()
{
int i;
for (i = 0; i < 10; ++i);
printf("%d\n", i);
}
test.d(5): Error: use `{ }` for an empty statement, not `;`