Comment by pimeys

Let's consider that you create a serverless platform which runs wasm/wasi code. The code can do an infinite loop and suck resources while blocking the thread that runs the code in the host. Now, with a fuel mechanism the code yields after a certain amount of instructions, giving the control back to the host. The host can then do things such as stop the guest from running, or store the amount of fuel to some database, bill the user and continue execution.