The ferry has a lot more room for food service. Can you imagine 50 people lined up in the little space of a Talgo Bistro trying to get their morning coffee, with just one attendant able to run the cash register and serve food? I would imagine that the space for food service on the Staten Island Ferry is equivalent to the floor space offered by THREE Talgo cars - and that doesn't include table or actual dining space.
Here's the ferries: https://www.siferry.com/currentvessels.html
The ferry line takes 25 minutes... although it also serves beer. I can see getting a quick bite to eat while you're a captive audience. Coffee in the morning, beer at night...