An assistant once tried to get me to use the self service till, instead of waiting in a short queue. When I demurred, she said "It's nothing to be scared of..."
I'm not scared of the thing, I just prefer not to use it. I don't mind a few minutes waiting, it's good down time, and I develop a Zen attitude to it.
Also, as Cudzo says, there's often a queue for the self serves anyway, and if anything goes wrong, you've got to wait while someone with no idea about till tries to figure it out, and then has to call for help anyway.