Lots of people, while waiting in a queue, switch off because they switch onto their mobile phone.
Problem is they get so engaged in what they are looking at, they miss the queue is moving and most of all, they are then too busy to engage with the sales assistant.
The sales assistant has every right to ask them to stop using the smartphone or miss their place in the queue if they are on their smartphone, they should be getting it ready with their credit card details or their bank app. But oh no, they wait till the end then try and find those facilities
Just bloody maddening and unfortunately the customer service person is not game.