No, it's to offload the burden/liability of being accused of shoplifting. If a cashier messes up, it's on the store. If you do, it's on you. Thanks but I'm not willing to assume that liability with little benefit to me.

I use self checkout all the time and have never been accused of shoplifting. Other stores in other neighborhoods might be different, and I wouldn't be surprised if skin color makes a difference too.