And stability is important, but not critical - and the main way they want to achieve it is that errors should be very obvious so that they can be caught easily in manual testing. So C++ style UB is not great, since you may not always catch it, but crashing on reading a null pointer is great, since you'll easily see it during testing. Also, performance concerns trump correctness - paying a performance cost to get some safety (e.g. using array bounds access enforcement) is lazy design, why would you write out of bounds accesses in the first place?