The issue with microHDMI is that, you will always need to use an adaptor for it, which makes it indifferent from carying around a usb-c adapter all the time like other devices. A full sized HDMI port would be awesome, as you wouldn’t need to cary around any accessoires at all.
I can see why a dedicated display connector would be useful in general, for example if all the usb-c ports are already in use and you just need an extra display.