In the beginning, BTC could be used to exchange of low value of virtual items, such as buying web sites or game points, virtual items, etc., afterwards, some people in order to get these virtual items, items may be in online auction own reality for BTC, others want to buy the real goods, but no BTC at hand, and then use real money to exchange BTC, as a result, BTC begin to flow, and have a "value".
In other words, bitcoin is inherently valuable as a means of payment; If it loses its function as a means of payment, it becomes worthless.
The value of money: it exists because of payment.
Like what most post says, it doesnt have to a currency to succeed. It only has to hold the a certain value. That's basically why it's digital gold. The very reason why people arent using it as much as we'd want to is that it's too volatile. It's risky for both the company and the customers transacting in bitcoin. Plus not all companies are equipped to accept it anyways.
Additionally in terms of inherent value. Its value comes from being a solution to a problem. As long as banks monopolize the financial institutions there will always be a place for bitcoin.