It can be, if you want it to - that's the whole point. Much like there are people who play WoW to accumulate gold, or PvP rankings, or raid success, or epic gear, or a working guild, or to craft all of the recipes, or something else I've not encountered.

The fascinating thing to me is that WoW's success was predicated on keeping people playing by paying content creators to come up with new goals for players to strive for, but minecraft demonstrates that people are more than capable of creating their own goals and successes within a sufficiently open ended game. For me, it was a lava moat. Then a pitched roof. Then a farm. Then a railway that took hours to build (and didn't go anywhere useful in retrospect). Then... etc