Self-checkout things get hit with lots of credit card fraud, the cameras help when the fraud gets so big that it's worth investigating.
Turns out he was hitting up the local home depot self checkout with credit card dumps he bought online, and picking up 100 $50 iTunes cards in less than 2 hours.
I ended up referring the guy to someone with higher risk tolerance, but I hope that gives you a better understanding of the scale. That's simply not possible with conventional checkouts.