What is the economics of the incentive system for data storage vs cost of storage? For the miner who mines a block, he only needs to store the additional data

What is the economics of the incentive system for data storage vs cost of storage? For the miner who mines a block, he only needs to store the additional data in the block. But the commons of the miner network needs to store all data, so isn't there a tragedy of the commons? Perhaps the number of miners would continue to wind down until only a handful can actually service the network, reducing the security and usefulness of the system. What incentivizes a miner to actually store the data anyways? Are there proper incentives to ensure that miners or whatnot actually continue to store all that data? The right incentive system would allow users to pay for data downloaded. Not sure if that's in the spec or code.