The supermarket I went to in the 90s boasted in their adverts about how if there were more than 3 people waiting in a lane they'd open another till. That's how bad the general standard was.

It's only faster because they took space and staff from actual checkouts.

The time saving is hugely illusory. You really should take your watch and measure. What costs most time at a staffed register checkout is mostly the payment. The staff scans much faster than you.