Anecdote of one: I bank with Wells Fargo, I go inside the branch less than once per month, and I rarely see the same tellers or "bankers" (the ones that sit at a desk) from visit to visit. I think it's pretty high turnover. I don't know the reason, but I suspect it's because the bank is trying to sell me services like insurance, and there's pressure on bankers to make sales. It may also be because a teller or banker job is a young person's first career-like job, from which they move on and up as soon as possible.

In fact I hate it when I have to talk to a banker, I get annoyed when they try to sell me services that have nothing at all to do with what I went in for, or with why I'm a customer in the first place.

Also, I suspect because of turnover, they usually can't answer my questions when I ask. They just do not know the answer to "how do I do this particular bank-like thing" without researching and asking the branch manager. But man they do know all about their insurance products.