@garrett I'll add a couple of reasons more:

- Many trains have groups of four seats around a table. Great to travel with a group. Bring out some board game or a deck of cards along!
- In Europe a ticket for a long distance train usually includes riding the local commuter trains in the origin and destination areas. Sometimes this covers other local transport (tram, bus, metro) as well.
- Sleeper cars in some overnight routes.

...and probably I'm still missing some