[ranger_danger]

Because you would have to assume too many things.

What if the GUI bring-up required mounting filesystems that need a kernel module that hasn't loaded yet?

What if the filesystem is on a network?

What if the network isn't up yet?

What if someone's xinit script needs access to the bluetooth stack which isn't up yet?

And even if the all the "correct" assumptions were made for a default install... doing anything different from that would require unraveling a mess to fix.