It’s not faster. I don’t know the numbers for every single vegetable I buy, and even if they’re on the sticker, looking at them and using the touchscreen is slow. When the clerk does it, they know all the numbers and it’s way faster.
That's a problem with the specific machines you have access to. Where I live, I just pick the vegetable/fruit/whatever by picture. I don't have to put any number in, other than how many of that item I bought.
I bet in 5 next years, self-checkout registers will be equipped with neural networks allowing them to recognize product standing on it based on camera input and weight, either allowing you to pick between items it thinks it is, or entering it manually. There is already technology allowing for that, it just needs time to be developed into it.