The reason for the 404 is because by default no action is bound to / in the proplists for the priv/<appname>.routes file. It tells you that quite succinctly. Explicitly heading to /greeting/hello works, as shown in the quickstart. Modifying the routes file is a good next step.

Your complaint boils down to there not being a pretty "Welcome" page. That could be addressed, but it's hardly a major concern.