Sprite sheets vs Zip files

[Inthegrave]

I never completely understood why sprite sheets have been the preferred method to upload on the site, the reason I always 
heard is that they are nicer to look at and quicker to approve, I get those points but overall they are more of a hassle to make 
and use. While a nice zip file can have all the sprites exactly as intended and you could even provide animated gif's for animations
saving the customer the hassle of trying to properly animate them. 

The only advantages I see for sprite sheets is that they are nicer to display on the site then a zip file but other than 
that they are a waste of time. 

Also let me just say that people can upload whatever they want, I just simply am wondering why Sprite sheets are preferred. 

I just figured I would open up a discussion because I find it an interesting thing to discuss.