Because it's disorganised, unstructured, and relies on another barista to info-dump everything about the job in the span of maybe 3 days. And that's assuming the barista who trained *that* barista even trained them right, and so on and so forth.

When I was a new barista, my store's SM at the time trained me, and he did a piss poor job of it. I used my breaks to go in and read the manuals front to back, and he gave me a book of recipe cards to take home and read (all super not ok and definitely not something I'm encouraging here). I essentially trained myself for free, for a $9/hr job lmao