I agree that there's a difference between hoarding and having enough in your home that you wouldn't go hungry if you had to stay home for a couple of weeks or if the supply chain failed for a while, etc. To me, hoarding is having a bunch of stuff you wouldn't eat unless you were starving, or having so much of something that you can't finish it before it goes bad.
I think it's just easier to have a good supply of all the staples, so i don't have to buy rice, beans, pasta, flour, etc. every week at the grocery store. It's also cheaper to get a lot of those things in bulk if you have the space to store them. Making my grocery list is much easier when I don't have to consider whether I have enough of the pantry staples, and even though I do meal plan for each week, if I happen to spontaneously decide to make something, I often already have the ingredients to do so.
I haven't had trouble getting what I want/need all at one grocery store, although like someone said above, I'm not particularly brand-loyal, and most of what I buy comes from the produce section, which no one seems to be hoarding! It also helps to have enough cooking experience to know what you can substitute -- if they don't have zucchini, I'll get yellow squash, etc.