Frontend developers and their tools

I read some frontend developer magazines like
net magazine and Web Designer Magazine.
Now I really like both of them, and so I thought about how great it would be to have something like that for backend developers (or maybe full stack developers).
And I thought about why it is that no such magazine exist.
Then it struck me how seperated the backend developers are vs the frontend developers.
I have seen many frontend developers who jumped from python to .net to ruby or whatever.
On the other hand I don't see many backend developers jump around like that.
A backend developer would be considered as a ".Net developer" or a "Ruby on Rails developer".

So one could not make a magazine with Ruby, Python, .Net, Objectiv-c etc. and sell it. Cause each type of developer would look for something in their own space.

That is a little funny to consider - I know I am stereotyping here. I myself have moved from c++ to perl to c# to ruby, and have done a lot of javascript in between.

But I still see a lot of backend developers being struck in the stigma, that "you can't just switch tools and platform like that!".
Why is that?
Frontend developers seem to be a lot more agile when choosing tools - they simply find the tool that works for the current project. On the next project another tool might work.
I even see backend developers moving to the frontend, and suddenly they are Ember or Angular developers (or backbone or...).

Now don't tell me that frontend developers are doing less complicated stuff - Responsive is for instance pretty complicated - so what is the reason that they (frontend developers) are so much more agile in the choosing of tools?
Have I maybe just met the wrong sort of backend developers because I have been in the .Net space for too long?

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