Why do we feel pressurised at the checkout ?

You get to the checkout and the assistant is sliding that food over the pricing sensor at 100 miles an hour.
Now….you try to keep up with the packing but faster they come….all of a sudden it stops…. she presses the public adress system “supervisor to checkout 9 please” she bawls out !! Now all this time the line has backed up with three people with trollies packed to busting and acting like the have a plane to catch in five bloddy minutes.
A bar code could not be read !!! Big deal,in two minutes it will all be sorted…........not a big deal for you? but for those behind….well it’s the biggest fucking hold up in the world…..tut tut tut tsk tsk tsk….evil stares from the pregnant mother,glancing looks of distain from people you have never met yet they really do not need someone like you holding them up.
Not your fault the bar code was faulty but to the people in line you are public enemy number bloody 1!!!!!
Finally it’s over you are free,it’s all packed and paid for and as you leave the checkout as your blood pressure drops to a safe level and you face melts back to it’s normal shape you look once again at the line and think what a set of impatient xzysv.
Do you get this happen to you or have i lost the plot here?