Integer overflow is relatively easy to detect and protect against at run-time using -fsanitize=signed-integer-overflow. (yes, needs testing. Doing it reliable at compile-time is hard.) But compilers also offer various options on how to deal with overflow. The users choose -O3 over other options. ISO C does not favor one over the other. But making it defined behavior that wraps would turn it into subtle correctness bugs which one can not easily screen for.
It's possible to just leave it undefined, without introducing unwarranted assumptions, such as that i + 1 is positive if i is positive, made in the absence of any assurance that i < INT_MAX.
