This is not really true, at least for the northeast corridor. Amtrak is the fastest way to get from DC to NYC for example due to traffic in the city if driving or taking the bus, and the distance from the airport (LGA or JFK) to the final destination in the city if you're flying. I take Amtrak somewhat begrudgingly because it often can be way more expensive than flights which are subsidized generally speaking over passenger rail these days, because it's simply faster.
And I honestly don't know what adventures people are talking about, most people keep to themselves. I've had more stranger experiences on flights than I have on Amtrak but maybe it's different in the West Coast.
I spent the entire trip on the Acela Express first class (work was paying) from NYC to Boston talking to an absolutely fascinating man headed to his 60th MIT reunion.
I spent the entire trip (including a 4 hour delay where we didn’t move) in the cheap seats from Atlanta to New Orleans smelling the farts of someone with serious GI issues while a college kid walked up and down the aisle spraying axe body spray to drown out the smell.
This only applies to sleeper car routes. You're on the traib for 2-3 days, mostly with no cell service. If you eat in the restaurant car, they will seat you with strangers. If you sit in the observation car, there's a bunch of other people sitting there too.