You have one unfortunate story, but I have the opposite positive story. As usual, it means that people are not all the same - and what works for one doesn't necessarily work for another.
What's your bodyweight? Are you carrying a bit more weight than is ideal? Did you have any previous injuries with your legs/knees? (Yes, we know that now.)
I suspect that you weren't snowboarding for a fraction as many hours as you were standing, so it's not really surprising that one activity hurt and one didn't.
I spent four years standing 10-16 hours a day - or rather, standing/shuffling/dancing. Not only did I not develop problems, but my lower back pains (from sitting) went away. And for the last few years I've been standing at work and doing pretty heavy weight lifting. I still feel great, and I'm in my 40s. I hope my story does as much to encourage people as yours does to discourage them.