Comment by metanonsense
Comment by metanonsense 20 hours ago
I think the issue it the (literal) "head-of-line blocking". Some requests can be processed either "concurrently" like tapping a beer from a keg or in parallel by having multiple bartenders, but having all people standing strictly in line makes this difficult.
Certainly in Irish pubs you wouldn't want the queue blocked while waiting a few minutes for a Guinness to "settle" before it can be served.