You learn pretty much any skill because it's in demand and people will pay you to do it. Of course there are some things you'd rather do or not do independent of money, but it's a good place to start.
A better question would really be "What factors would lead me to believe C++ is right tool for a particular task?" Which, I think requires a bit more depth than you'll find in this article.
As the author of the article, I can only say that I agree with you but I just wanted to write a little bit longer version of "Hey, look, C++ is alive and there are still interesting jobs involving using it!".
Your question is something absolutely different, and yes, it should be given much more in-depth thinking.
A better question would really be "What factors would lead me to believe C++ is right tool for a particular task?" Which, I think requires a bit more depth than you'll find in this article.