From the downloads page: > Please note that both the Mac and Windows version are very large, as they contain Raspbian, the Raspberry Pi operating system. Therefore these downloads may take some time to download, depending on the speed of your internet connection.

Perhaps overload, but there you go!

Makes sense for a non-technical user (One not versed in Linux-Fu) oriented software.

It could be made to download the distribution from the internet, but that introduces more failure states you'd have to handle and explain to a user in clear language.