The Home app on MacOS Mojave is just a iOS port using UIKit. MacOS doesn’t currently have the integration required for HomeKit hub control which would be coded down to the metal. It’s likely a security nightmare they will address with future iterations of MacOS and potentially hardware depending on how iOS and tvOS handle HomeKit Acessory Protocol (HAP).
It destroys the battery on my iPad Air 2 so that maybe a factor as well when it comes to laptops.