I've never seen a grocery not carry baking powder, well at least at the times I've needed it.
It's the difference between men and women, I guess.
I suspect that if the man in the house did the grocery shopping, grocery bills would be cut by more than half.
I give you the example of this couple, my neighbors. When the whole family (husband, wife, three infants) is at home and the wife does the grocery shopping, she spends $200-250 and an hour or so doing it.
When the wife is visiting family in Omaha, with or without the infants, and the husband does the grocery shopping, he spends circa $80 and twenty minutes doing it.
A woman, considering shopping recreational, likes to look around, and is thus enticed, seduced, by pretty packaging and "placement of product."
A man, for whom shopping is a drag, an utter nuisance to be done as quickly as possible, knows what he wants, or needs, before he goes into the store, gets it, and comes out as quickly as possible. He sees only those things he wants or needs, ignoring all else.
Myself, being a man, am not acquainted with 99% of the products even in the modest grocery store (six aisles) in town because it's stuff I don't need or want.
It's the difference between women and men, and I'm not disparaging women--without women, none of us would be here, so all hail! to women--but just telling it like it is. If a man doesn't need or want something, he doesn't see it.