Comment by jolmg

They don't make a race of it, but I think they go at a reasonable "marathon" pace. There are also dedicated baggers. I should note that cashiers also accommodate other services like paying utility bills, or making withdrawals from one's checking account.

It's not just about speed, though, it's particularly about the unified lane and the fact that 2 self-checkout stations easily fit in the space of a single human cashier station (that may be unoccupied because of a store's hiring budget). It's also about peoples' patience. If a store hires less cashiers and enough people are still willing to wait in line such that there's profit, well...