I've struggled with this topic when trying to explain bitcoin to friends.  they literally will ask why it is worth money.  I often times struggle to come up with a good answer, however I know why it has value.  It's because we all believe it is worth something.  It is a way to circumvent the banks and not give all the wealth to the rich.  It gives us a way to have a ledger for all transactions that occur using bitcoin. but more than that it spurred a movement, it has opened up countless financial opportunities for new businesses and technologies.