Why do dwarves only have a racial base of 3 tokens?
Because their power continues to work in decline, Dwarves are not intended to be played for very long. In most cases probably 2 turns with them is all you should be doing. Get 2 or 3 mine spots, and move on to your next race. This is why there are fewer Dwarves, because you aren't intended to use them for more than a couple turns or to conquer more than just a few spots.