Do you expect Rails developers to have their own pet projects that they put a lot of time into? I agree it would be strange if no one had any forks, had never done a pull-request etc.
Pet projects? Absolutely not, although never a minus. ;) More: are you engaged with the community enough to be aware of the current ecosystem, (handwaving) "best practices", libraries/gems, etc. If someone claims to have been building Rails apps for 5 years, but has never heard of Devise and Carrierwave, it's definitely a red flag for me. If you're trying to get a job on the Google search team and can't whiteboard a quicksort it's going to be an equivalent red flag for them. I'm trying to attract a specific type of developers for a specific kind of programming work where caring about this kind of stuff is useful as a signaling factor to me.
It's not about requiring everyone who works for us to be a 23 year old with no family or life who spends every night hacking on shit, just about a baseline standard for community engagement. Lack of Github account with some level of activity (even if that's just starred repos, forks, etc) is a pretty strong indication someone wouldn't meet that level of engagement, and so wouldn't be a good match.
