It was implied. Why else would you use that argument in responding to ridgeguy's comment about using human-run checkout lines? What machines would you point to as making the world worse?

In any case, since it bothers you so, you explained the situation yourself: "The self-checkout is there because it is cheaper than a cashier."

It's an error to equate "cheaper" to "increase in standard of living" because the people benefiting from the reduction in cost are usually not the entirety of the community, and it's unfortunate that someone of your caliber accepts such lazy thinking.

Over the last twenty years, automation has increased but the standard of living has gotten worse.

You both miss the crux of the argument, i think. It would be more precise to say that physical machines raise the standard of living that we measure, but abstract machines reduce that which we don't measure. (Viz, finance.)

Compared to a generation ago, we can stuff more crap in our pockets and wardrobes, but housing is precarious and public institutions are weaker. Good luck supporting a family on a bottom-quartile wage.

GDP, measures of inflation: Goodhart's law.