Enhancing Arc is fun, writing practical apps in it is not. Open source developers go where the fun is.
As for your next question ("Why is enhancing Arc fun?"), it's because Arc provides many tools for manipulating Arc code (macros, code-is-data), and few tools for writing applications (libraries). The implementation is also fairly simple, vs. trying to hack on Java or Python or C++ compilers. Path of most impressiveness per unit effort seems to go through porting it to another language, rather than writing another webapp that'd be more impressive if done in Rails or Django.
Comments
Enhancing Arc is fun, writing practical apps in it is not. Open source developers go where the fun is.
As for your next question ("Why is enhancing Arc fun?"), it's because Arc provides many tools for manipulating Arc code (macros, code-is-data), and few tools for writing applications (libraries). The implementation is also fairly simple, vs. trying to hack on Java or Python or C++ compilers. Path of most impressiveness per unit effort seems to go through porting it to another language, rather than writing another webapp that'd be more impressive if done in Rails or Django.