1. Infrequent departure times. There are about 100 flights from New York to LA a day. Plenty of departure time options. Are there going to be 100 departure choices with a train? No, it would probably be 15 at most. In Canada, we have relatively fast rail between Toronto and Montreal, two of our major cities. Even with similar travel times all in, they struggle to get people on the trains because of the lack of departure times. There are about 50 departure time options by air.
If you can have 30 people a pod, then you can have tons of departure options or even could be flexible about them.
2. 367 miles per hour is slow for a country the size of the USA. That is 7 hours point to point from New York to LA. Probably 11 hours with stops and not being able to go that speed along the whole way.