you answered your own question there. the community isn't bothered about the popular image of PLT Scheme as merely a Lisp for teaching. (whether they should be

you answered your own question there. the community isn't bothered about the popular image of PLT Scheme as merely a Lisp for teaching. (whether they should be bothered or not is a whole different question, but choosing not to care ensures that PLT Scheme won't be a mainstream Lisp.)