Or they have blanket rules, specifically so that people can't make reliable inferences from their behavior in specific cases.
There's even a standard joke on this, IIRC the setting is some sort of court case:
"Did you sleep with Joe on Monday?"
"No."
"Did you sleep with Joe on Tuesday?"
"No."
"Did you sleep with Joe on Wednesday?"
"I refuse to answer that question."
"Thank you."
If you are innocent and care about how your company is perceived, you don't have blanket rules. If you are guilty, blanket rules are the easiest way to deny the problem.
There's even a standard joke on this, IIRC the setting is some sort of court case: