[racket] raise vs abort

Hi again,

I'm not sure where to ask this question, but
why are 'raise' and 'abort' implemented separately
(rather than, say, 'raise' by means of 'abort')?

I haven't understood the implementations of these primitives,
but they appear very different (in error.c and fun.c).
Will someone explain to me why they should be, roughly?

Keiko