As a customer (and a stockholder) my concern is getting in and out of the store with as much ease and speed possible. Adding the self service doubles the actual check out ability and those six people can cut meat, cook chickens, shag shopping carts or stock shelves instead. It is not "anti-employee" but is a good, competitive business decision. Just look at their track record for expansion, growth and popularity. Don't you want to keep your membership costs under control?
Actually, Front End Cashiers and Front End Assistants CAN'T do all those other jobs, unless they are hired into one of those positions in those departments. There are very specific job categories that aren't interchangeable. And if the particular location happens to be a unionized warehouse location, the restrictions are even more specific.
As to Self Check lanes, wait till you (or the person in front of you) have a problem or need assistance with something, and then tell us how convenient it is. Self Check customers have no reason to hurry along. But the regular Front End Cashiers are timed on how long they spend with a given member. It is literally tracked in seconds. If they are too slow, they are counseled about their performance. Three such counselings in a six-month period, and the cashier is taken off the register.
Costco tracks employee performance very closely. The guy at the door who checks your card coming in has a clicker in his hand, and he reports door counts every half hour. That tells management how many cashiers to have ready to step on to a register if needed. Self Check messes with those numbers in a big way. The result can be fewer available payroll hours for cashiers to work, which can reduce their paychecks. It's not a matter of "letting them work elsewhere" in the warehouse. They could be working themselves from full time down to part time, if there aren't enough hours available to schedule. And if the door counts are down, management starts cutting people loose early, and sending them home, which also reduces payroll hours and paycheck dollars earned. It is not a simple science.
I've been a Costco member in one form or another since 1982. (I started with Price Club, then Price-Costco, and then Costco.) My spouse has been a Costco Staffer for more than 25 years. There is a LOT of Costco talk in our household. And whenever the topic of Self Check comes up, it's a mixed bag of responses. Some people like it, some people hate it. At the end of the day, the members are the ones who will have the last word. In my experience, a qualified, fast Cashier who is focused on doing their job will get through the cart in front of me in a hurry. Then I can get my few things, and get out of there. Self Check lanes may seem faster, but when the member doesn't know where to scan their own items, it slows everything down. (The same thing happens at my local grocery store.)
What I wish Costco would install is an Express lane, for the people like me who only have one or two items at a time. That would be a time saver.
Dave