"It is a kind of twisted reasoning "
Although I disagree with it, I do understand the logic behind it. The companies doing this are usually capitalist, not virtue-driven. They don't care about morals, laws, etc. They screw over their customers in any way they can get away with. They also do things that cause their customers problems but lie to them about the reasons. Self-checkouts make the customer experience worse for most (not all) customers. When they add them, they usually do a staff cut followed by telling self-checkout workers to push customers to check themselves out. Nothing is given in return for the extra hardship. It's just a middle finger to the customers that made them the money to buy the machines (or invest in better customer experience) in the first place.
So, some are following that "do whatever I can get away with that's in my self interest" mentality giving them the middle finger back. Funny enough, in my area, most of these companies with poor security in their self-checkouts are nickle and diming the people that run them on top of increasing the number of machines they watch or side jobs they have to do on top of self-checkout. I had to wait a few minutes earlier today for my self-checkout clerk to stop bagging at a register to fix a problem on my self-checkout. Needless to say, that kind of crap just adds to opportunities for people stealing or just walking out to buy their stuff somewhere with fast-moving people at registers. I've done the latter many times since a trip to convenience store was faster than the lines at similar prices.
I'd be more outraged if it was someone ripping off Publix, Costco, or Aldi.