You have to be one kind of stupid to casually travel with that much cash and a whole 'nother kind of stupid to tell the person you're sitting next to that you're doing so.
And dont forget that, at least for some people, 100k is chunk change. Maybe they are heading to a big poker tournament with other 0.1%ers.
You're civil, aren't you? Or were we just caught thinking with that side of the brain again?
Contrary to popular belief, there are in general perfectly reasonable people out there to talk business with in transit.
Not every person you meet will be "civil", despite appearances.