The Ralphs near me, in SoCal, does. I was tired at the end of a long day of managing 3 sick kids and a sick wife. In my absent mindedness, I had 17 items in the 15 item self check out. I had to get a clerk to come over and authorize it for me.
That's one thing. Then there's loss-leader sales limited to "2 per customer/family" or some such because they know someone would fill up their cart with it.
Of course, if you self-check out and pay cash, they're less likely to spot you with the reduced supervision of self-checkout.
...or just use self-checkout and ignore the limit.