Increasing the block size makes the blockchain harder to decentralize, and in the end, it doesn't solve the problem, but just kicks the can down the road. It just doesn't make sense to store every coffee payment forever in the blockchain. That's why the focus is on security and decentralization, and let second layer solutions deal with the payments problem (privacy, latency, throughput). That's the plan for now, until someone comes up with a better idea.