Sprite sheets vs Zip files

[Inthegrave]

The reason is simple. Not everyone visiting the site are looking for sprites to use for their own project. Many (myself included) just like to browse the site and look at the artwork. Sheeted content makes this easy. Zips need to be downloaded and extracted and as a result, aren't really useful as far as browsing goes.

Sure, but they just make it more of a hassle for people looking to use them, It is a hassle for rippers and users.
The reason you provide only benefits a minority and hinders the majority.

Sprite sheets only seem to benefit browsers and site staff, no one else as far as I can see. 

I can't prove that the majority of people use the sprites, but I have a feeling that most people come to use not view.