I guess the really big problem probably is that there is no canonical implementation, no obvious way to go like there is for other languages. When you want to play with Java, you grab NetBeans or Eclipse and you have Sun to turn to for a runtime. When you want to play with Ruby or Python or most newer languages, you go to http://{$language}.org.

Smalltalk suffers from the same problem - too many different implementations, and no obvious path to follow.