Fear of shortage is part of it. I get it even if it annoys me. I needed to get some just to get some more (we're down to one 6 pack Kirkland upstairs which is about the time I would normally purchase more; sometimes doing that at two 6-packs left), I'm not interested in stock piling it just was looking to replenish.
If news articles would ease off on writing articles day after day about concerns these past few weeks people wouldn't feel as anxious about it. That anxious feeling is what drives people to purchase it even if they don't need it. Then it becomes like a light switch, one day you're okay and the next you get this panicky feeling like you need to get the stuff now. Just about everyone at Costco this evening had a Charmin package in their cart. Most of them were likely purchasing Charmin because KIrkland wasn't available. People weren't really stock piling on other stuff; seeing their carts normal levels so it's not, yet, like it was in the spring when it was a run on just about everything.