OK, and I'm the one generalising yes? Clearly you have zero bias towards the Rails devs.
How about simply becoming really good in a skill instead of jumping stacks every 5 years? To REALLY become good in Rails, to the point where you can write gems for activerecord for example that do something cool with arel, or follow the work Tenderlove is doing easily, this type of good takes effort. and time. Some people don't care at all and will happily switch and rebuild that expertise (or will never become experts in anything). That's totally fine. I value expertise, and won't make the switch for something that on the surface doesn't look like will benefit me at all (again, concurrency as it is in Rails is just fine for my career path and I think most Rails devs are on the same boat).
If you prefer that melodramatic phrase. I've been a Rails dev for 6 years and I know that many current Rails devs don't dare try something else -- call it a survivorship bias, fear to abandon what pays the bills now, habits, and most of the time you won't be wrong.
Every now and then I speak with some of them and we exchange ideas.
And you should stop stereotyping, it's juvenile and definitely has no place in HN.