Because the shelves are empty, I'm guessing far more reasonable people are thinking to just pick up a single pack when they do see a store stocked. Just in case they miscounted the amount they have at home. But when you count the number of items of TP on the shelves and compare it to the number of families, there is a large mismatch. Far more families than TP. So even a minority of those families making the quite reasonable 'buy one just in case, not like it will go bad' decision will quickly leave a store bare, meaning the rest of the day is filled with shoppers seeing bare shelves and thinking 'next time I see some, I should grab one just in case'.

While there are some panic buyers who are buying far more than just 1, I wonder if they are making as much an impact as all the non-panic buyers who are just picking up one just in case.

Maybe not, I could be off on the impact, but it does seem reasonable at first glance and explains why even purchase limits can have a hard time combating TP shortages in the short term.