Earlier quoted context omitted.
Why must all software developers be able to operate in all domains? What other industry has a requirement such as this? There's more than enough work out there, why must a web dev know or care how to twiddle bits, or vice versa?
Did you ever worked ? In all companies I worked for (I'm a researcher) I had to use different languages: java, c, c#, asm 86, perl, python, ruby ... Honestly it's almost a requirement to be able to adapt to other languages or at least read and understand what it does.
Not that they couldn't, but why would you?