How about the concept of control? I would hypothesize that people prefer self-serve at banks, gas stations, and checkouts because they are in full control of th

How about the concept of control? I would hypothesize that people prefer self-serve at banks, gas stations, and checkouts because they are in full control of the situation. If they've been there multiple times before, they're familiar enough with the system that they can navigate it quicker than having someone else do it for them, and any inefficiencies they can only blame themselves. Also, there is a certain effort that goes into human interaction, the smiling, greeting, small-talking, and being polite so you can (hopefully) get them to treat you better and do a better and faster job on your requests. Or you can just do it all yourself and save the trouble.