Because my shopping included a bottle of wine.
Often pop to my local Morrisons for small top up shops. Popped there this morning to buy a few bits, including a bottle of wine. DD aged 3 likes to 'help' me at the self service checkout, scanning the shopping, and then at the end I lift her up and she uses my debit card to make the contactless payment, or puts the coins in etc.
Today as I was about to lift DD up to pay, the lady overseeing the checkouts rushed over to stop me and said DD wasn't allowed to pay for the shopping. She said it wasn't allowed as then the alcohol could actually be for her, or the debit card could actually be hers. When I pointed out that DD is only 3, and the debit card was mine, and it was clearly me really paying for the shopping she said it didn't matter 
AIBU or is this completely bonkers? I could totally understand this if I had an older teenager with me but it feels like there is no common sense anymore 