If you want to build such a big, worldwide financial network, you need to accept the fact of taking different kinds of costs.
The same thing is about decentralized network, it has to operate somehow. If nobody will earn anything on supporting it, then what is the point of doing such a thing?

Without mining rewards, bitcoin and blockchain are pretty much totally different thing. We need to have a bounty for people willing to confirm our transactions, or they will simply stop doing that activity.