Another difference from the "old days": Back then, if your train got stuck in a drift for 6 hours, you would complain about it to your friends and family once you got home. Now, you'd be breathlessly live-Tweeting/Facebooking/Instagramming it and within hours the whole world would know about your plight.
If you are a PR person, you'd rather have disgruntled people be disgruntled at home or in their hotel room, rather than stuck out on a train somewhere, or having to camp out at a station, etc. I'm not saying that's the only factor in whether to cancel service, but it's certainly a piece of the equation.
Possibly, but there are plenty of people stuck in airports from time to time that can tweet up a storm.