Like sticking a man on the moon or trying to cure cancer the answer is simply "because it's something to do".
Actually, 1) they got rid of the lego start icon, fantastic and 2) with the searched fixed and unified, I actually uninstalled Star8. So far so good. The more granular snap with dual "monitors" helps, it multitasks better and snap views stick per session (and I hardly ever reboot). I'm not missing too much but you definitely need the Start Buttons to get to the start screen. I have a dedicated start button on my Logitech touch zone mouse but often it's quicker to just mouse to it believe it or not.
This is definitely one where people are just removing it, just because. What do you need to put there instead again?