I'm pretty sure that is the sole purpose of Minecraft in general? Without building, it would be a pretty crappy game I think.
A Minecraft without building would still be pretty good, you've got a whole world to explore with caves and stuff, and you can still fight mobs.
But there is no point in exploring a cave or the world if there is nothing to do with it. Minecraft would just turn into a crappy definition Dungeon Defenders.
Well, for some people, maybe not, but it would still be an awesome world with a whole lot to find. It would be more of a freestyle, leisurely game without building.
But the problem is, with Minecraft there is only so much to find. It would be fun to new players for a while, but for veteran MC players it would be pretty much like this. Oh yay, it's my 5th forest Woohoo, I found lava (for the sixth time)
