>visit hp.com/plus-support for additional setup help
My guess is that the person in question bought a model/sku that operates not as a typical printer (ie. you pay for the machine and its consumables), but as a printer as a service model[1] (ie. you pay per pages printed). In that case it does make sense that you need to install the app (presumably to connect the printer to the internet and to connect to your account) for the service model to work. I don't see the issue with this as long as this was clearly disclosed on the box when the printer was purchased.