Iv seen posts with people substituting rape with r@pe. Other than bypassing filters I can’t see a reason to censor just 1 letter that doesn’t actually censor the word? I see if you fully censor the word, but even still context completely ruins the censorship.
I would assume it’s mostly habit from platforms with content filters and uncertainty if usage of the word is prohibited despite a lack of filter. And then a dash of “online subculture”