I am pretty sure that there is a hidden purpose of bitcoin rather than being a coin.
It was developed, it solves bysantine problem but purpose? People will give purpose to it
Since the author is unknown and he had no paper declaring the mission and vision of the said bitcoin project we have no fix and definite purpose that really defines the intention of the creator. Yes, you are right that people, the users who are using bitcoin will give purpose to bitcoins existence. There are many theories as why bitcoin was created here are some weird opinions:
1. Bitcoin was created by big time syndicates so they can do transactions without being monitored by any law or government organizations. It is black market money.
2. Bitcoin was created in an effort to escape from the tyranny and slavery of the present financial system. It is made without a center to free the society from the harassment of the banks. It gives freedom to the people to enjoy their investment and also the interest coming from it. Its main intention aside from being a revolution currency it tries to replace fiat currency and rewrite the world financial system.
3. Bitcoin was created by the creator simply because he wanted money, he even hide himself so that no one will accuse him of being greedy holding a huge volume of bitcoins. Nonetheless he created bitcoin for profit.