That's utterly wrong comparison! Overall complexity of natural languages is probably HUNDREDS times the one of programming languages. Excluding C++, maybe. And also, with time you begin to be much more efficient in learning languages (that's true for natural languages too!), when it makes no sense really not to learn new languages.
That being said you don't really need more than a handful languages (selected for their adherence to various paradigms, as my sibling suggest) if you're not interested in inventing your own language.
You don't need to learn all the programming languages, either.
Get a glimpse of a few to discover new ways of thinking, but specialize in a handful only.