Yeah. I think the "I don't fly" market is also underestimated. People who use trains as practical transportation because air is simply ruled out for them, whether because of fear of flying, medical conditions, dislike for the TSA, or "carbon emissions shame". I'm in the "I don't fly" category and there turn out to be a lot of us. Just medically diagnosable fear of flying apparently affects 6.5% of the population, which is about 2 million people.
"Train vs. Car" is the option for these people.
I think your math is backwards. 2% of the population would be 6.5m or so (there being something over 300m people in the US). 6.5% would be around 20m.
The thing is, when we first started looking, the train was not even a consideration - we were checking flights ... not trains. The train didn't enter the picture until we had trouble finding a flight that fit her budget. We did not gloss over any negatives - we just don't view as "negative" the same things you view as negative.
It's called family ... always willing to help
On the first bit, that is almost identical to my first overnight train trip: I was initially going to fly to Florida. I checked flights (admittedly, I fumbled the search because it was pretty much my first self-booked trip and since I was going to "Daytona Beach" I didn't think to look up "Orlando", and looked up a one-way fare) and found them insanely expensive (IIRC it was $500 for a one-way flight down). I promptly turned to my grandmother and asked if I could look at Amtrak, which was about $150 or so each way. Sold.
As to family, that works if it works for their schedule. Friends are in the same boat. For example, I've got a reasonably reliable ride to/from Richmond (Staples Mill) or Norfolk. However, he's currently in the middle of a two-week work project that basically knocks him out of doing that (unless it's a damned big emergency). Having Uncle John do a pickup is all well and good unless he can't get off work that evening, and not all of us have large families "in the area".