See the El Cheapo Airlines thread for a Greyhound/Amtrak tangent…
My contribution, which speaks to “Why would people take the bus?”:
If you want to really see the country instead of flying over it (or driving past on a freeway), Greyhound or Amtrak is the way to go.
Even before Covid, I was trying to avoid planes (and the demeaning TSA/check-in/seating experience) , and trying not to put any more money in airlines’ pockets. I even turned down far-flung conferences in favor of ones I could drive to.
But I’ve found that when I drive, I don’t get to just stare out the window like I’d prefer, AND the quickest route is around cities on generic-looking freeways.
But bus and train stations are often in the more colorful parts of town… or at least the more industrial (in which case the color is rust). I loved taking the train cross-country and seeing a lot of cities “from the backside”.