Btw, I am angry at the moment because of this incident (which might make some people saying they're easy and that we don't 'have' to use them understand a little better where the rage comes from).
I was going through Heathrow last week, and I had a boarding pass with a barcode on, placed inside a holder which also had a barcode on the back of it. I have very little visual memory and I struggle to work out which symbols relate to what. The boarding gate required that you scan your barcode, and the screen flashed up a moving demonstrating of how to do this, which I couldn't process at all.
After struggling a few times, the woman working the gates called across 'you with the red bag, you need to do it properly'.
I asked could she come and help me, or could someone scan it for me, and she said no. Despite the fact a sign said that if you didn't have a boarding pass with a barcode, you could ask to be checked through manually, so obviously the option existed.
Eventually she came over, and turned out I'd been scanning the wrong barcode, which I would not have worked out. Her response when I explained I genuinely found it very hard to cope with lots of visual symbols? 'Oh, it's just like the self-service in the supermarket, which everyone uses'.
I really could do without it being assumed that these things are easy for 'everyone'. They're not.