Because racket isn't as easy to get running on smartphones as something that just compiles to C.
With gambitc you are already there.
I know that, with Racket's move to the Chez Scheme interpreter, bits of core Racket C code are getting rewritten in Racket (https://groups.google.com/forum/#!msg/racket-dev/2BV3ElyfF8Y...). I wonder if that might enable Racket to ultimately be able to run on other Schemes' infrastructure.
> with Racket's move to the Chez Scheme interpreter,
Is there a wiki or an issue to track progress of this?
I don't know. I'm only familiar with it because of the Google Group posting and associated Hacker News story from a while back.