I queue at traditional checkouts all the time.
I don't get paid to do their job and I don't get any discount for doing that.
Queues at checkouts started when they closed the traditional checkouts and opened the self checkouts.
Remember when supermarkets had dozens of checkouts people?
No much to queue at the time.
We're allowing machines to replace us in everyday life and this can only be a bad thing.
Look at kids nowadays: apart from the school hours, they have zero interactions with humans, that's why they're socially handicapped.
They use machines for everything, even to chat to one another (social media).
Then they panic when they're faced with a human to human discussion in person.
I see how slow people have become in analysing and respond to simple arguments and this is because we don't interact as much as before.
Some time ago I was "caught" by an employee of a managing company of my old friend's block of flats, throwing away a makeshift bed that some drug addicts had prepared in the communal shed area.
She accused me of theft by finding

When I asked her the definition of theft she started panicking.
Then I told her that she needed to call the police because I was committing an offence.
She moved on saying that I was breaching health and safety legislation by throwing away "contaminated" items.
I asked her what act of parliament she was referring to and after a couple of "elf and safety" nonsensical answers she started crying.
An old woman listening to this hilarious conversation simply said "leave it, she's gonna have a panic attack in a minute".
And that is how inept most people have become socially.
A lot of people can't cope with reality because they're used to online interactions where you can say whatever you want and then simply not reply to the answers/questions that follow.
My advice: forget machines, deal with humans.