That information is misleading. It is not the same to work for a small company/startup one rather to land a job on corporate business. Stack Overflow is misleading and it is biased however it is far from the real world.
In my country:
ruby: 38 jobs.
Freelancer (online jobs)
ruby: 20 jobs.
C# : 225 jobs.
Practically, 1/10 of the jobs of c#.
But, you could say "but X company uses Ruby...!". well, that's not the trend. It's cheating to consider an exception while ignoring the trend.
I need 1 (one) job at the moment. Just make the best companies in the country to headhunt you, and feel free to choose the language by being most pleasant.
Or you could pick JAVA, where there are more chances to find a job, stable and a better salary.
Now, I gonna shot some myths.
Stack Overflow has limited usability, it means to usage and statistic. Most of the businesses that publish on Stack Overflow Jobs, simply collect information and database. Why do they do that? I'm clueless but it is the typical help-wanted that never answer.
However, even when Stackoverflow-jobs is limited but it the trend of StackOverflow (question)
tiobe.com/tiobe-index/ This ranking is debatable but it marks a real trend.
So I repeat, Rails is like the "second best store in town". So, why not we pick the best one?
And Ruby, Ruby does not work alone, we have Ruby and Rails, so we must learn Ruby AND Rails at the same time. However, and it is the surprise, Rails is for cheap works. Most companies that preach that they use R&R, they use Instead Ruby and Sinatra, maybe they used Rails (at some point) but later they jumped to Sinatra. There is also Grape and Rack, they beat Rails to the death. You don't need to trust me, you could google for that.
So why people pick Rails?
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.