“...why isn’t guilty or not found on the threads where the genders are reversed?”
It has to do with the origin of the practice, and the meaning of it, which is not what the “offended” posters around here seem to think it is.
The origin of the practice comes from an actual court trial where an attractive defendant was deemed to be too pretty to be guilty.
However, FReepers now broadly use the term “guilty” or “not guilty” to acknowledge the attractiveness (or not) of someone’s picture in lots of threads, not just those that deal with court proceedings.
It’s funny when used in threads about Helen Thomas. It’s not funny when used in threads about pedophile teachers.