Why doesn't B12 from seaweed get much attention?

A small pack of thin seaweed wraps like Gimme's provide 140% DV of B12. They're very low density (only about 30 kcal each) so someone could easily eat 2+ packs in a day. Yet it seems rarely mentioned that they're a good natural source of B12. Almost without fail whenever I see an article or discussion of B12 intake in relation to veganism it's that only animal products naturally have B12 so to get it from supplements or nutritional yeast. Am I missing something?