OK, so after being away from mountain biking for a few years, I go to one of the two LBS's in town to learn about the whole 29er thing. The young sales lady makes a good guess of my height and pulls out a Giant in a size L to take a look at. When I throw a leg over the thing, the top tube only provides an inch or so of clearance. Other than the comically short stem, the thing feels like a road bike. When I ask why my old 26er had gobs of clearance and this doesn't, she can only offer "because that's the way they're supposed to fit." So, what happened here? Why were we told that we needed a couple of inches of clearance for so many years and now we don't? And what's with the short stems? The young sales lady's reply, "because you're supposed to be more upright." What's behind these shifts in frame sizing paradigms?
Should've mentioned: I'm 6' tall and looking at getting a hardtail XC bike.