MTB certainly lag behind road bikes for desireability right now. I suspect because of two simple reasons: they are not as old, and they have not been co-opted by the fixy/hipster crowd.

But still, its hard to find a nice lugged one. I have bought a number of old MTB's and frames in the last few years, and while I have a handful of nice ones, I only have run into a couple of lugged ones.

jim