If you're looking to save a few dollars, it can certainly be left off and you can just use the stock Intel cooler that comes included. But for the price, it's a good value. While we mostly wanted it to improve the look of the build through the window, it will also typically run a bit more quietly than the stock cooler.
Rook mistake: I ordered the evga G3 version and a slightly different G-card, the VGA Asus Dual-GTX 107008G GTX 1070. I only noticed when I was following your video to build it. I just powered it up as a test before cleaning up the cabling as in your vid, and it seems to run fine!