I believe Minecraft would be better if there were missions in survival mode. It would give it way more purpose than to simply build a house and survive with it. I am aware of achievements you can receive for doing a few things, but I think a lot of us would like some in-game reward for accomplishing a task. It shouldn't be as easy as "chop down a tree; reward 1000000 diamonds", it should be something like "Enter the Nether; reward _some useful item_"(food,tool,etc).
The cons of this would be the trouble of coming up with the missions and rewards, but the pro would be that it's more entertaining and more challenging. Some people believe it's challenging enough, and I agree to an extent. If you think about it, the only goal you really have is to build a house and gather as much ore as you can. With the missions in place, people would be more into the game, more enthusiastic about it. They would also get the feeling of accomplishment after completing a mission, especially if it's hard or takes a while to do. Please give me more insight on what you think of this idea (why it could/couldn't work, why you do/don't like it, etc), I'm open to all opinions. Thank you.
Different goals and rewards are already built into the game... you're just failing to see them. For example, the reward for entering the nether already... is access to the various resources that are only available in the nether. One goal in the game important to survival is to establish a brewing station; and a blaze rod is needed to do that. So, to gain that "achievement," the player has to enter the nether and kill at least one blaze mob. Handing people a "useful item" in addition to the resource reward already built into the game would just make the game easier, not harder.
The principle behind a "sandbox" game is that YOU make up the goals and challenges for yourself. If just building a house and surviving isn't enough for you... do it in a treeless world. Still not tough enough, up it to hard difficulty. Still not enough, make slaying the end dragon a goal (and no "cheating yourself" by looking up mineshaft locations using an app... or by X-ray glitching to find your stronghold.
I agree that rpg-like missions/quests are not needed. If you wanted to make a case for more achievements to earn, I would support. Lots of players like to knock out all the achievements, and some that are more creative and/or advanced might induce more players to branch out their style of play and discover more of the game. They could do this by reading the forums, but not everyone is so enlightened...
Another poor lost soul in the world of minecraft. Too blind to see that this world is his own. If only this player had imagination, intuition, or an idea of how to get them. Maybe than, will he unlock the true meaning of life in this multi-verse.