For very socially 'dependent' games like The Sims Online, crafting and trading can be a very nice thing, in that it allows you to give gifts to other people on special occations, or gain new friends in the game by helping newcomers by giving them some tool(s).
But it can also have this effect in more 'teambased' games like WoW, though the social impact might be a little more lax. But hey - at one time you might give a 1000 DPS sword to a dwarf when he needs it, and then you become friends (or you already are friends), and then next time you need 1000 gold, he'll carve some out the mountain for you!