It's not taught to apes because it's simple. It's taught to apes because apes cannot physically speak, and so teaching them Esperanto is likely to be fruitless.
--- On Wed, 7/15/09, Chuck Grimes <cgrimes at rawbw.com> wrote:
> So there are a lot of political overtones to using ASL in
> primate
> studies. What? We're monkeys? You think our language is so
> stupid, you
> can teach it to a monkey? See those are the political
> overtones.
>