It is more important to have a faucet by the outside A/C unit (same goes for an outside outlet). Just like James says, it determined by age. I at least note it in the report when there are no outside faucets.
Point out its absence without regard to when the house was built. Give your client the “heads up” on the inconvenience before they discover it later, on their own.
We have a county here in CO (Park Ctny) that does not allow outside faucets. They are usually placed in the garage, but can’t be outside. It s a water thing here.
There is no requirement in the IRC for any exterior faucet whatsoever. If there is only one, I generally let them know and if there are none I definitely let them know.