Why does battery drain when Surface Laptop is completely shut down?

I shut down my Surface Laptop 7 with Intel completely with the battery at 100%. No hibernation, no sleep—complete shutdown. And yet, my battery seems to drain. I don't use my Surface very often since my daily driver is a MacBook, but after I turn the laptop on again after a week, the battery percentage is down to 78%. Why would a Surface Laptop use any power in shutdown state? Shouldn't the laptop simply be "off" then?