Those auto-installers backs up the installed script only periodically. The backup option in cPanel allowed you to make a full cPanel backup with all settings, files, folders etc. In it self not a huge issue when a single user at a time doing it, but when a large number of users decide to do that at the same time, it does cause for high resource usage. Free hosting does have a few thousand users per server, which is the main reason it is not an option to have it available for free hosting.