They NEVER had a mother/son activity. And during the period when I was most active, I had a 12 - 15 year-old son. I would have loved to share an activity with him. I asked and asked when they were going to have a mother/son activity, but never got a response.
Oh wow, that is the identical thing I complained about when my older son was the age of yours. I believe that it was done deliberately to keep female influence from the boys of priesthood age. It was Ok to have den mothers, but nothing beyond age 12. Wouldn't want the boys to be tied to their mother's apron strings, now would we. Why they might turn gay, or not go on missions, or, or?