Could someone explain to me what the point of home sharing is?
It depends what type of person you are.
Camp 1:
For someone always on the go, it doesn't make a lot of sense. You'd rather sync your devices together so that you can watch whatever you want wherever you want on whatever device you have at that time.
Camp 2:
For someone always at home, you don't want to waste the time syncing everything. Put everything on your main computer (where storage is not an issue), and watch it anywhere you want (upstairs TV, downstairs TV, outside on my iPad, or on my computer or TV in my den).
I'm in the 2nd camp, and this is exactly what I've been dreaming of - and the Apple world with AppleTVs and airplay is amazing!
Plus, it's now so much easier to watch something I find on the internet to my TV. I don't want the hassle of connecting my laptop to the TV.