It's irreversible, which is one of the main things, plus it's practically a debit card, instead of a credit card, plus it's an asset that's profitable if you hold. And it's always accurate and quick in transactions. The system is well secured.
Bitcoin is different from fiat. If you hold it, the value will increase. If you use it, the value will also increase.
people holding their coins and the price to go up makes sense, but i don't see how actual usage will increase the price? to be more clear, usage in what way? spending as in buying things at merchants accepting bitcoin? if so, then it won't really help in increasing the price as the coins get converted to fiat directly as merchants use payment providers such as bitpay to handle all transactions.