

Boston to NY is more like hourly - Amtrak has a lot of trains going on the line from Boston to/from DC (DC also has a very good transit system for the US at least from what I’ve heard).
The problem with those trains is that they’re expensive and slower - the Amtrak northeast regional costs $75-300 (depending on the date and time, as Amtrak is a company and charges more around holidays and during peak travel hours 🙃) each way from NY to Boston and takes ~4-4.5 hours. Driving can take 3.5-4 if you plan around rush hours in both cities.
The Acela (faster one) is also several times a day now, but it’s more like every 2-3 hours instead of 1