It's not about one language and one issue... it's about being able to solve problems regardless of tools given (i.e. programming language)

We don't code, we don't write code... we solve problems with code... there's why.

And if you're not eager to learn all of these... you should think about a change in careers

Problem 1: I can't get this damn div to float to the right of my content.

Problem 2: My network card firmware stops acknowledging commands from the driver after 3 days of high utiliization.

If you think you would assign the same person to "solve these problems with code", you're being silly. People specialize and gain expertise in their areas. Use the right tool for the job.

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.

Indeed, I did ever worked. Of course you need some breadth of knowledge, but unless the place was absolutely tiny, your low-level developers writing VHDL weren't going to be asked to optimize a SQL query or tweak CSS.

Not that they couldn't, but why would you?