This really may not be as bad as it sounds. Just as brothers used to spend the whole day working in foodservice, I was one who sometimes spent the whole day in the money room, counting money and preparing it to go to he bank. 2 or 3 of us in a room all day, and stayed 3 hours after the session ended as we were still counting. Other brothers periodically took the money to the bank. I and other brothers could easily have pocketed hundreds or even thousands of $ each convention. There was always a concern about getting held up. Yes we all worked in small groups but a thief would just need a gun and take the $. When you used to give $ to the brother in the parking lot or at the literature desk, he could have been pocketing some of it.
A family attending the convention likely would have budgeted a certain amount to bring. Instead of having to carry so much cash, they can use their credit card for food, gas, and hotel, so why not their donation too? And they can pay it off the next month and not have to pay interest on it. If a gang were to go in with guns and hold up the entire place, they would not get much cash. Just jewelry and equipment. And brothers don't have to stay locked in a room all day + 3 more hours, or risk their lives transporting thousands of $ to the bank in their own cars.