I don't recommend trying to walk while crouched. It's easily hard on the knees, and those are kind of important. In video games, though, you can do that for days, no problem.
I've mostly been poking fun at Fable 2 in Parable, but that game said "hey, remember the stealth options in Fable? Yeah, we don't need that."
And to be fair, they didn't. It wasn't that fantastic a thing in the first game, and the way the second game was structured, I don't think it would have added much of anything to it. Fable 2 was mostly about fighting swarms of things, and you only got XP via defeating enemies or consuming items, so you'd just be missing out on core gameplay and experience by trying to sneak past things.