I think the aim was more for supportability. I assume if you enjoy Scheme; you would like to write more of your language in Scheme and less of it in C. Although

I think the aim was more for supportability. I assume if you enjoy Scheme; you would like to write more of your language in Scheme and less of it in C. Although that is somewhat contradicted by the plans to create a new syntax for Racket going forward. Chez Scheme by itself seems to be extremely fast.