- Making decent gear for your main character to supplement quests and drops. Personally, I like wearing gear that my toon has crafted.
- Making good gear for alts.
- Making specific valued pieces for friends and guildmates.
- Making consumables to buff you.
- Having something to do other than quest and kill. Collecting recipes and advancing your crafting skill is fun.
Crafting in WoW is not good for:
- Making money by selling crafted gear to other people.
I think a lot of the people who have problems with the crafting in WoW had visions of, say, becoming an weaponsmith, and selling the weapons for large amounts of profit. But the simple truth is that crafting gear is not a good path to riches.
And the reason for this is straight supply and demand. It is very easy to become a crafter, and thus are a lot of crafters in WoW. Almost everyone has at least one crafting profession. This quickly forces the margin for crafting to a very low point. If I have materials for something, and you charge 100g to combine them, I can very easily find someone who will do it for much cheaper.
As well, you can get gear from quests and instances, so crafting isn't specifically necessary. Also gear doesn't degrade, so there's never any repeat business. If player X buys a Sword of Doom, she's never going to buy another Sword of Doom, only a Sword of Greater Doom.
Realistically, the only way you can make good money from a crafting profession is to have an extremely rare recipe that is highly valued. In the old days, this would include epics like the Lionheart Helm.
Blizzard has tried to build a little bit of margin into crafting in TBC, most notably with Primal Nethers. Primal Nethers are bind-on-pickup, so if you want an item that needs one, you need to find a crafter with the recipe AND a nether she is willing to part with. That imposed scarcity allows the crafter to increase her margins on crafted goods.
If you want to earn money using professions, the best thing to do is focus on items that are used up. This includes consumables and raw materials used in crafting. After all, if everyone is a crafter, everyone is going to need materials. Supply and demand.
Now, is this situation good? Would it be better to make it so fewer people are able to craft, allowing them to actually make money from their profession?
Personally, I like the existing system of crafting. It's very solo friendly--until you hit the Primal Nether stage--and I like being able to make gear to supplement my quest gear. I can live with not being able to make a profit via crafting.