I don't think I need to explain why it's unintuitive that multiplying two unsigned numbers sometimes results in a signed multiplication, even though signed types appear nowhere in the code. I couldn't tell you how many times I've seen some DSP application taking uint16s and throwing them into a filter without realizing it could be UB.

Language standards shouldn't rely on compiler options to save developers here. There's a lot of compilers in the world that don't support the same range of options GCC and clang have, like CompCert. Those are often the ones building safety-critical applications these days, where trapping would be inappropriate.