Disney makes it seem like you'll be able to handle everything with just your MagicBand.
Want to buy something? SCAN YOUR MAGICBAND!
Need into your room? SCAN YOUR MAGICBAND!
Want Mary Poppins to clean your house? SCAN YOUR MAGICBAND!
(I made that last one up.)
And, while that is true for most things, it isn't for everything.
Unfortunately even Disney World requires IDs sometimes - like if you want to purchase alcohol. Yep. If you want to "drink you way around The World" you're gonna need an ID.
Planning on using your Annual Pass for discounts? You're gonna need an ID.
And, while it is true that you can pay for *MOST* things with your MagicBand, system errors aren't unusual and you'll be left high and dry and unable to buy that churro and adult beverage if you don't have some backup cash or card on you.
I hate seeing sad faces at Disney World - especially adults sad because the scanners are down and they can't get that frozen Grand Marnier slushy drink thingy in France.
DO NOT BE THAT PERSON. Bring your ID. And some cash and maybe even a backup credit or debit card.
MagicBands are a perk for staying onsite.