In many cases, I am faster than the available cashiers at my local grocery store, because they're old. Also depending on what I'm buying, idc how my stuff is bagged so I can just throw it in a single bag and go vs them taking 3 bags to do the same thing.

But to me, the main reason to use self checkout is that I don't have to interact with anyone. No conversation, no upsells, just me and a machine. The only reason I'll go to a cashier is if I have a lot of stuff or if I'm buying alcohol.