Nothing really prevents you from checking in your downloads in to a github web project though and hosting via that though (but probably not the fastest solution).
This is kind of a relic feature back when people compared github to SourceForge. Github is collaborative source code hosting (open or private projects alike) and not really open source project hosting.
So, with GitHub, I can use the fancy git tools, I've got bug reporting and issue tracking, I can make a website about it, but I can't offer a download that's not a snapshot of the repo (barring any silly workarounds)?
Pages are definitely a development tool. Most of the time, (when some lazy dev isn't using it as their blog!) they contain useful documentation and instructions for other developers.
This is kind of a relic feature back when people compared github to SourceForge. Github is collaborative source code hosting (open or private projects alike) and not really open source project hosting.