The problem with that, is that the depth of github is pretty hard to fake. Sure, you can have repos with code in them, but the time of day you commit, what your commits look like, how you work, is well documented.
Note also that this is the same for private repos hosted on github. When you are logged in, you can see the activity and commits of yourself (and your teammates) in all of the public+private repos that you have access to, but your public profile only shows public commits. This is by design.
Here is my example image, when I was doing a bunch of work at the start of the year in some private repos: http://imgur.com/4Tr3LQz The top is my public activity and the bottom one is my public+private activity. So if you're used to working out of private repos, then nothing is publicly documented and your actual github profile is not very 'deep'.
All of that is true, but my point is that you can't just gin up fake repositories to look good on a resume.