I don't know why he never did, especially after the whole April thing.
But there's too many secrets like Peter, Reilly, and Kaine keep the whole clone thing secret from Mayday. Reilly and Kaine keep Reilly being Darkdevil and Ben's son a secret from Peter, MJ and Mayday (even if everyone notices how similar Reilly looks to Peter). Reilly and Mayday don't know Kaine is Peter's clone.
If everyone would just come out in the open and say everything it would make the Parker family reunions so much better.