For better or worse, our current hardware architectures present a shared memory interface for intercore communication. So if you want a non-toy CSP programing language you have to implement with a programming language that support shared memory concurrency (for the OS at the very least).

And of course any sufficiently complicated message passing program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of shared memory and coherency[1].

[1] Yes, the reverse is also true.