This is a very valid point. The economic systems of GRC (and most of crypto) are still begging for development. The community is having very active conversations on how to build mechanisms for the GRC ecosystem.
One idea is a Gridcoin managed BOINC project that runs on a business model that involves purchasing GRC to crunch work. This project is working with the title MicroGrid for now and is in the early stages of planning.
Below is a recent podcast that discusses other possibilities with regards to building up the GRC ecosystem and economic mechanisms.