Because it has to complete with English which is already a world language(at least in the business world)

And Lojban is better anyway. ;-)

http://en.wikipedia.org/wiki/Lojban

http://pinstack.blogspot.com/2008/02/top-7-reasons-to-learn-...

http://www.lojban.org/tiki/tiki-index.php?page=Lojban+Introd...

There is an answer to that question:

http://www.xibalba.demon.co.uk/jbr/ranto/

Esperanto is not particularly easy to learn, despite the claims of its founder, so learners devote their time and effort to learning languages with much more return on investment once the language is learned.

Or even, why isn't every language written using the latin alphabet?

To which an answer might be, latin doesn't support certain sounds, can't represent tones... and if it did, it would break chinese language interoperability.

Analogy with human languages isn't ideal, because they have almost all grown up organically, whereas programming languages are, to a large extent, designed. The reason that every language doesn't use the Latin alphabet is, amongst others, geographic -- so many others grew up in isolation from the West, they'd never come across that alphabet before. The same isn't really true of programming languages.