Because that one is included in the free fantastico scripts included with the cPanel brand of control panels. A couple of cliks, enter a username and psaaword and it's ready to run. No ftp, no MySQL setup, no muss, no fuss. Point, click, load and go.
As is everything you see listed on the right side of this page -
http://www.affordablehoster.com/mini_site.html
Why go through all the crap of loading a script when they have an auto install sitting waiting.
I do use the ftp type install with CubeCart, because it's a new version. And I've done so many I can do them just about as quickly. Still have to set up MySql by hand, where the fantastico auto-installs do all of it. CHMOD's and all.