I can at least understand where the impression might come from. To me it seems that compared to many programming language ecosystems, Racket has much more "language tooling" in relation to other features/libraries. For example, sometimes I wonder if it's worth it to have so many for forms instead of providing a base for the most common uses and leave the rest to the language users in case they need more. (This could be by combining simpler for forms with other code or use named let.)
I think part of the reason for all the language tooling is that macros and #langs make it relatively easy to write such tooling. So people attracted by this possibility turn to Racket and write more and more such code, which again attracts more people interested in that and so on. 
I can imagine that some of the professional developers do much more "PL research"-ish things than in other language ecosystems even if they're not being paid for PL research and hence might not be seen as PL researchers. 
This topic actually reminds me of some of the discussion in this thread.