Because lots of companies pushed their graphic artists and designers into UX roles without providing any training, expecting them to learn on the job. I saw it happen at every job I’ve had and heard about it from people I knew at other companies.
I don’t think work training turns you into someone who thinks logically about systems and about human psychology.
In my experience it doesn’t. I came at UX from the interaction design/HCI side of things so I was already generally that kind of person, but the people who came at it from the design side weren’t as strong weren’t as strong. They were still very good at design though.