You should read the introduction of this article about this "mere curiosity".
"French is the second most widely spoken language in the European Union and the second most widely learned language in the world, but despite its strong international position, the outlook for French in Europe is not so encouraging. Over the last four years, the number of French-speakers in the continent has fallen by 8%."
It has of course been supplanted by English as the lingua franca.
French is still prominent in large parts of Africa but is facing increasing competition from English and Arabic.
The huge number of human languages is a product of a bygone era of isolation. A Darwinian process has ensued that is seeing that number constantly whittled down and outside of truly primitive cultures (there are still people in the world living effectively in the Stone Age) I imagine within 100 years you'll see a smaller number of languages spoken by a larger portion of the global population.
[1]: http://www.euractiv.com/sections/languages-culture/french-la...
4% of the planet. If 4% of America spoke a language, most of us wouldn't be in much of a rush to localize.
Fortunately for French, the core native speakers in France are rich, and most of the planet is still poor. As the rest of the planet catches up, "curiosity" becomes more accurate over time.
If 4% of people only speak a functional programming language, does it mean that you never need to learn one? Just because the vast majority historically speak imperative doesn't mean it's the best for your business. Same for OSes.
Diversity is source of wealth.
Plus those numbers only account for speakers who can read and write. As I said in another comment, the alphabetization of Africa over the next few decades is expected to boost these numbers significantly.
So, as the rest of the planet catches up, "curiosity" becomes LESS accurate over time.
By the way, I'm not french, and I find that "curiosity" term insultingly patronizing.
You're implicitly assuming that the remaining 96% of the population is speaking another language which is untrue in your analogy as the world population speaks more than one language and the largest one in terms of number of speakers goes to Mandarin with around 15% of world population.