Probably they don't care, I don't know. Why would you care to hide your stats?
There's one reason which comes to my mind. That is, if you post a comment a forums post by you're ratings which can be silly in some regards.
What are your considerations about that?
I looked online for a good bit, and found requests for this feature dating as far back as 2016. Is their an actual reason chess.com hasn’t added this as an optional feature, or did they just not see/care?