Has anyone out there ever heard of anyone forgetting to light candles (not “ones” but forgetting)?
It’s not that hard to imagine in the hectic rush to get ready for Shabbos, a harried woman could lose track of time.
It could also more easily happen when she is not in her usual routine, such as away at a simchah.
A case where sge arrived home (or whatever her destination) too late to light because of negligence would also fit the category of “forgetting”.