The fear is that a cartel of big, centralized, have-huge-data-pipes miners would drive out smaller miners by forcing up the block size high enough so the smaller miners have to drop out.
Price discovery of bandwidth is the solution.
A bandwidth market can lead to an efficient use of bandwidth but may do nothing to address the potential tragedy of the commons concerning decentralisation.
Users want their transaction to be relayed to miners.
Miners want the transaction to reach them so they can earn the fees associated with those transactions.
Miners want other miners to receive their blocks to have their reward recognized by the network.
Users want to receive the block the miners produces to they can know the state of the network.
I submit that pursuit of just these policies would actually encourage centralisation. A small number of large miners will consume fewer resources than a decentralised mass. A single trusted data centre could be even more efficient.