Little bit of both? Also probably to prevent the temptation of theft. Even though the fee is nominal, it seems to be enough of a detractor?
If it really was about stealing (taking and intentionally keeping), the 1€ or free plastic coin you can get at the counter wouldn't deter you at all.
Most homeless and poor people know this trick. It really is just for general populace who are too gullible to know better.
I know you didn't mean it this way but this is an incredibly funny way of putting it. "The globalists don't want you to know this, but the shopping carts at Publix are free..."