Stan: From a retailers perspective sometimes it is impossible to predict the amount of customers that will come though the door at any given time then on top of that what if you have a few staff sick? Sure you could employ more staff to cover this but you as a consumer will have to pay more to cover this.
The problem is most people want bottom dollar pricing, top notch service, high stock levels of product and increasingly a higher living wage. It's not possible.
I'm very happy to pay for top notch service. Indeed I prefer to pay for it. In terms of food retail (and indeed most other retail), however, there is no national chain that offers that model in NZ.
It is not impossible to predict - you just don't do thin provisioning with your staff. If I walk into (say) Whole Foods in the USA or Waitrose in the UK, I won't find a shortage of staff unless there are exigent circumstances like a flu epidemic and even then they would try very hard to overcome it.