The main implementors of Racket and Chez Scheme (Matthew Flatt and Kent Dybvig) were part of the committee that created the R6RS, and many of the ideas in R6RS

The main implementors of Racket and Chez Scheme (Matthew Flatt and Kent Dybvig) were part of the committee that created the R6RS, and many of the ideas in R6RS came from Racket and Chez. Whether R6RS was "widely rejected" is of course up for debate, but the people that didn't like it decided that mostly after Matthew and Kent's contributions. https://ecraven.github.io/r7rs-benchmarks/ https://ecraven.github.io/r7rs-benchmarks/ is an ok comparison between Scheme implementations; you can see that Chez is much faster than Chicken in general. Chez also already supports many features beyond Chicken that were needed to implement Racket (for example, internal support that made delimited continuations easy). It's hard to know exactly how many people use what, but it seems likely that Racket is the most widely used Scheme derivative.