I would much rather spend 2 or 3 days on Amtrak then spend 2 or 3 days on Greyhound or Trailways. Maybe 6 or 7 HOURS is my limit on a bus! (And even that is streching it!)
Without a national Amtrak, if the airlines shut down, how would you get back from Arizona to Rhode Island? Besides bus or walking? (Oh - driving for 5 days from your vacation in a rented car!)