#1 the reason that the first applications to trade bitcoin for were dollars, is one of the most normal things ever. If a new currency is created, the main use case is to transact it for something else, most likely the most abundand and usable "good" there is. In our case, this means that people want to transact it for the dollar, its arch nemesis. This is why exchanges are yet the most common usecase.
Discussion
#2 Things need time to grow, once more people will understand the importance, more manpower will work to enhance it. Right now alot of adoption is halted by wrong opinions of wrong bankers and others, who misinform the public for their own gain. But now, we are at the point were goods other than simple dollars are exchanged for Bitcoin.
#3 if Bitcoin would replace the current financial system overnight, no single government would need to spend alot of wasted energy on securing their own local currency trough war. Administration would be easier and verifiable, no wasted time on transporting banknotes or such.
The real-time price discovery that is possible with Bitcoin makes it possible for prices to immeadiatly respond to issues in the global market, real signals. Instead of paying a fraction of a cost for a shirt made by slaves in bangladesh, you would pay higher and thus be more responsible. The slaves in bangladesh wouldn't be slaves because they got access to their own property rights. This would make it more beneficial for everyone to not waste anything because they aren't forced to. Inventions and etc would also help people be efficienter and thus requiring less energy.
#4 Bitcoin mining is indeed centralized. Too much for sure, and other aspects of the network should also be more decentralized. But that is not its job: that is your job. This natural money is just a method of securing transactions economically and globally. How those transactions are carried is a different story, maybe yours.
We just need ways to transfer those bytes accross the houses, streets and the globe, a pretty simple task isn't it? Satoshi Nakamoto set already the right path by "the network is robust by its unstructured simplicity" and "messages only need to be delivered on best effort basis".
It is up to us to implement the best strategies for this.