Esperanto - why don't we use

I've heard that it has some

I think that no society will ever want to speak Esperanto as a national tongue because it lacks a corresponding culture.  Languages and the barriers they present often define a culture, shaping it and becoming a permanant and extremely important determining aspect of a nation or ethnic group.  If people gave up their language for Esperanto, it would be like giving up or deleting their culture.  Even if we in the US made Esperanto a second language, people in general would not be happy and would prevent its ever taking hold.  The English language has shaped our country's culture and world outlook to such an extent that it would seem ridiculous to most people (myself included) to adopt another, distinctly FOREIGN language.  However, I can see the country adopting Spanish as a second language in the future because hispanic culture and people have taken such deep root in American society that Spanish is now, well, very American! :)

Mi parolas Esperante flue. Oops.  I speak Esperanto fluently. 

While Esperanto is spoken by 2 million people, I really don't know why it is not even accepted by the E.U. as an official language.

No society is expected by us - Esperantists - to speak Esperanto as a national language. Esperanto is made for international communication, and we hope it will some day be the second (or third if there is a local, regional or religious language as the second) language for everyone. We don't want people to give up their culture,  and think that a neutral language will  be less damaging  to local culture than  English is now (and Spanish, Russian, French, German, etc were when and where used as international languages).

By the way, Esperanto does have a culture - literature, music, theater, etc .