Apple don't want to ruin their reputation of having fantastic standby times, which actually is a revelation when you get to experience it (it's fantastic to basically always be able to just grab your laptop and keep going where you left of).

A lot of (real) pros don't care about things like battery life and size, they just want something powerful and semi-portable running macOS they can do resource intensive work on while away from their desktop/something so powerful they don't need desktops.