There are open-minded and intelligent women in plenty on gransnet, but it seems they are just not that interested in sex phonelines. There are open-minded and intelligent men on here too, but none of them seem to be replying.
You also have to remember that since the school holidays began, there has been a spate of daft posts by bored youngsters who are under the impression that it is clever and amusing to shock the old dears by posting things about sex (oooh, how daring!) They underestimate the old dears - they are not so prudish after all, they are just rather bored with them. So when a new poster chooses sex calls for a first message, they get an automatic reaction - "Oh, not another!"