My number one reason for avoiding self checkout is that I want people to have jobs.

If fewer and fewer people use the manned cashier lines, there will be fewer manned cashier lines.

If it's busy, and I'm just grabbing a few things, sure, I'll divert to the self checkout, but if there's nobody in line, or just a few people in line, I'll avoid self checkout. I'm not going to be the reason someone lost shifts.