First, the fact that Bitcoin can be used as a type of currency cannot justify its value. For something to be useful as a type of currency, it must satisfy all the following conditions:
1. It must be fungible.
2. It must be easily divisible.
3. It must be easy to exchange.
4. It must be a long-term stored value.
Your first two points muchly applies to the fiat currency economy while i so much go for the third and fourth point in which i think they are best applicable for bitcoin, what you see in bitcoin may not necessarily be what others exactly see in it but bitcoin value remains valuable, appreciative and profitable enough for everyone who key into using it the right way, it has been used for store of value, why is because anything that has the tendencies and capability to rise in due time is worth investing on, while its acceptability is global and fully decentralized.