There are two things to remember about bitcoin, they have different environments.
Some people live in countries that will not protect legal contracts and that won't protect the value of their local currency. For these people, bitcoins are a transferable asset, and this gives them utility. It's similar to gold or to US dollars. It's a barter good. It's got value because it's valued elsewhere and you can trade it. These are places that learned that trading in cellphone minutes was a good way of conducting trade.
Some people live in countries that WILL protect legal contracts and protect the value of their own currency. For these people, bitcoins then just become a source of speculation. You don't *actually* want bitcoins because of any underlying use. You just want them because you're hoping to trade them for the thing you actually want - namely, more of your local currency.
The developed nations could undermine the value of bitcoins with one simple piece of legislation. "We will not legally enforce any contracts involving bitcoins." And, just like that, they'd have no value. No notable value, anyway. Every single speculator in developed nations would have to do oodles and oodles more work just figuring out how to protect the initial transaction.
Bitcoin only functions because we spend our own tax dollars subsidizing courts to enforce contracts involving bitcoins.