Why hasn't Esperanto caught on?

Because the last thing Europe needs is another euro-language. It's easier to learn because it's deliberately made simpler - but it is still learning another language, and learning another language to any kind of fluency is still a multi year effort with thousands of things to memorise and practise.

As well as "no one speaks it" (approximately true), no areas speak it, no laws are written in it, no road signs are written in it, no maps, nothing to push anyone to learn it. And where not-using-any-agreed-interlanguage does cost, the costs are hidden or swallowed unquestioningly and the consequences brushed aside:

"An effective malaria control program would cost only $800,000 a year," says a French doctor fighting disease in Laos, "but there is no money to finance the operations. Simply no money. No money to pay the staff, no money to purchase equipment, no money to buy gas. There is simply no money." (5) But when the Twenty-Eighth World Health Assembly decided - against the recommendation of the WHO Secretariat - to add two languages to the four already in use, it accepted to earmark for its language services $5,000,000 a year, "to begin with" (6). It refrained from carrying out a cost/effectiveness analysis that might have determined if its decision would facilitate or complicate matters. As a matter of fact, observation of the functioning of international organizations shows that the addition of new languages entails for them only complications and added costs. True, a few States are put in a better position, since they can use their own language, but this involves no advantage for the organization as a whole, nor for most of the Member States. Yet, all international organizations have undergone the same evolution: they have kept increasing their language budget at the expense of the activities they were meant to perform. To save a child from malnutrition costs only $10 per year. This is the cost of one 7 word sentence in a document translated at the UN, (7)which translates many millions of words a year. - http://claudepiron.free.fr/articlesenanglais/effects.htm

Translation is expensive. In the oligolingual system, every thousand words in an original text cost US$2030 for translation in seven languages (average for UN and WHO), or more than two dollars per word (Allen, Sibahi and Sohm, 1980, table 7). Such a sum seems more realistic than the figure of 36 cents a word given for the European Union (Rollnick, 1991). Apparently, the European Union translates daily 3,150,000 words, so that translation costs there, in the most conservative estimate, US$ 1,134,000 per day (Rollnick, 1991).

The situation is quite different with the two multilingual systems, which rely heavily on translation and interpretation. With simultaneous interpretation, a loss of 10% and a distortion of 2 to 3 % are considered normal. The conditions are such that it is impossible to transmit a speech in another language without gaps and errors while it is being delivered. The interpreter must not only have a good delivery, a perfect mastery of both languages, a quick mind and sharp hearing, he must also be fairly familiar with the subject in order to repeat in the target language everything said in the original using the appropriate technical terminology and without dropping important elements. Such a combination of deep linguistic competence and vast technical knowledge can rarely be found. Hence the large number of inaccurate interpreters noted in UN documents (King, Bryntsev and Sohm, 1977, par. 89 and 94).

- http://claudepiron.free.fr/articlesenanglais/sociolinguistic...