I'm not entirely certain myself if artificial sweeteners cause insulin spikes, but it's worth pointing out the difference in numbers between high and low blood sugar. Normal blood sugar is what, 90-100 mg/dl or so, while the diagnostic criteria for low blood sugar starts at 70 mg/dl. Meanwhile symptoms for high blood sugar start above 200 (or even sometimes 300) mg/dl. Presumably cravings for sugary foods kicks in well above 70mg/dl too.
Simply put a spike in blood sugar due to a sugary food is much, much bigger than the drop in blood sugar sufficient to trigger a change in eating habits. And that's before we consider the impact of non-insulin hormones on our behavior, such as Ghrelin, which won't show up on a blood glucose test at all.