Of course it's useful. Why should something like cups get started without a printer? Why should the user know to enable it once they get one? These days hardware changes at runtime, and things are expected to work when you plug in a printer or a bluetooth adapter, and not to complain or stop booting if some hardware turns out not to be there anymore.
Cups should be started without a printer, because then you can print in a file, put the file on a USB stick and go to a print shop or a place with a printer
Or it may not know when an network or LPT printer becomes available.
That is a technicality, though.