Undefined signed overflow isn’t great (and it doesn’t help that C’s implicit integer promotion rules are bad), but it’s important because it allows loop optimizations, which really are important cross-platform, eg Intel is fine with loops counting up but PPC would like them to count down.

The problem causing this is that C loops are overspecified. If there was a “for…in” loop that didn’t make you declare and increment a variable, then manual increments could trap on overflow without causing so many problems.