This line of thinking I feel like assumes it's the only program running on your computer. Using less of my CPU and memory means my computer can do more things in parallel, or even run more instances of the harness. My laptop is sweating when I got 5+ claude code sessions running.
I haven't monitored CPU usage so closely, but seems to get heavy with basic tool calls and editing. Memory usage definitely is out of hand, have an idle session right now eating 500MB