Minecraft isn't an RPG. In the land of videogames, RPGs are NOT defined by the same qualities as a non-videogame RPG (such as dungeons and dragons). Though what does define them isn't really clear. Wikipedia had a great article discussing how they weren't the same under videogame RPG. But now it appears some numnuts (probably working for IGN or something) got rid of it and makes it look like they are similar. blah.
But anyway, back up to NES-era. There was a game called Zelda 2, you played as link, you got skills, you leveled up/had experience, it had NPCs (though they'd only say 1 line). Yet this was not an RPG, it was considered adventure.
It seems that nowdays people just don't even use the term "Adventure" anymore for videogame genres, instead they slap on "RPG", I personally don't even think dark souls is an RPG so much as an adventure with RPG elements (all adventure games have more RPG elements now IMO). Though it's definitely in the area where nobody should really fault someone to claim otherwise.
I should probably just give up, that wiki article said it better than I ever could >=(. Seriously, that guy should be hanged.