I posted a few days ago to praise English speakers everywhere. A reader asked why my opinion was of Esperanto. For those that don't know, Esperanto was designed as an international language that would be easy to learn, pronounce, read, and write. The idea was to provide a common way to communicate.
Esperanto never took off. I think there are a couple of reasons.
Probably the main problem with Esperanto, to use the business term, is that it has no installed base. Nobody speaks Esperanto, so nobody makes movies, books, or radio shows in Esperanto. Which means that there is little reason to learn Esperanto. It's a circular argument but the logic is inescapable. The only way to really get enough people to learn Esperanto to make a difference is to force them. That's why so many Central Asians speak Russian.
Learning a language is hard, and if you are going to take the time to do it, you'll probably pick the one that lets you talk to the most people, make the most business connections, and see the most movies.
Another problem is that Esperanto can't be easy for everyone to learn. Languages fall into families. For instance, most of Central Asia speaks Turkik languages including Turkish, Kyrgyz, Uzbek, Kazak, and others. These languages are closely related and it is easy for Turkish speakers to learn Kazak. Dutch and German are close, as are Spanish, Italian, and French. Spanish and French and Dutch and English are all closer to each other than they are to Russian. There is actually a fascinating field of study where the migration of people around the world can be traced through the family tree of the languages they speak.
What this means is that Esperanto must either be related to nothing, in which case it is hard for everyone to learn, or related to some existing language in which case if favors the speakers of that language. There is no way to design a language that is equally easy for both Chinese and English speakers to learn because their native languages are so different.
So despite best intentions, Esperanto is a language which is quite hard for some people to learn and which nobody speaks. It never had a chance.