That's the thing. Planning trips to Disney Stores isn't like planning a trip to Costco or supermarkets because when people shop in these type of stores, they're there to buy food and essential household items, so they'll make sure they bring enough bags. Granted, supermarkets still offer the convenience of bags - plastic (SU or reusable, depending on area) or paper, and outside of ordinance areas, Aldi and Lidl charge a benign fee for them. However, Costco has never provided bags from the onset, due to being a wholesale warehouse, so the majority who don't have their own bags would just simply cart them out. Disney Stores are neither warehouse clubs nor supermarkets (they're obviously stores that sell official merchandise), and because most are situated in malls or big cities like NYC, people will still need the convenience of a plastic bag, but the problem is that they're charging too much for a low-quality reusable bag that's prone to ripping apart, and is still often disposed of due to the quality of them, so they're unfairly profiting from such a bag that actually costs a huge fraction of a whole dollar to produce and is actually worse than the type of plastic bags they used that were still reusable and recyclable.
Getting there is just a small part of it. The biggest part is anticipating how many purchases you're going to make, and while that's not a problem for food shopping, shopping for anything else, particularly Disney merchandise, and especially during a sale, it's more difficult to predict, and even if you had the one reusable on you, chances are that if you suddenly decide to take advantage of special deals despite going in for just one thing, and your bag doesn't fit everything, you'd then have to purchase another bag, and 99c adds up a lot quicker than your city's ordinance minimum. And speaking of bag ordinances, I'm more in favour of charging ordinances than banning ordinances, though the majority, even San Francisco's, are literally just minimum plastic bag thickness laws (they're only bans on what the law defines as 'single-use' plastic) with fees rather than draconian bans like Kenya's that border on ecofascism, though as this isn't the place for politics, I digress.