Why would I use this when I can find a free script that doesn't require any sign up and does the exact same thing with more options?
P.S. The snow graphics are blocked by UBlock, if you're using it.
Animated things like this have been around for as long as I can remember using javascript on pages. If the chronology repeats, I expect we'll be seeing wobbly clocks following the cursor and notes about which browser you should use for the page soon.
I've seen snow on a few websites recently, makes me rather nostalgic.
Eager itself is a platform to allow non-technical website owners to install the all of the open-source and SaaS tools which technical people already have access to. If you already know how to add JavaScript to your page, Eager is more about convenience, not necessity.
Javascript snow (and other visual gimmicks like this) are client side; even Geocities would have let you host it yourself. Most hosted services let you add some form of Javascript/HTML code somewhere.