This problem has improved significantly in the past couple of years, I imagine due to Angela Ahrendts takeover of the stores, but I still find it annoying.
For whoever's downvoting: for starters, no paper receipts, no bags, no cash. With self-checkout that's all my choice. Not so with Apple checkout.
The self-checkouts are mostly for basket-only shoppers.
It would have been interesting if they'd thrown the self-checkout option into the mix. I suspect people self-scan much slower than a cashier, but given that self-checkouts occupy less space than a full till with conveyor belt, (hence a lot more terminals), I suspect overall they're still faster than using that space for normal tills.
The machines also have a pressure sensor that detects that you have placed items on it after scanning, if you don't allow time for the sensor to settle the machine will give an error and require a cashier to reset it.
Interestingly the same scanners can be used for the online order picking.