It makes sense from a plot perspective, especially if you believe the theory that the honoured matres were a team-up of the bene geserit, the fish speakers, and the tleilaxu axolotl tanks.
Just because the books mention or deal with sex doesn't mean they're 'horny'. There are no titillating scenes, no lurid descriptions. Sex is presented as a tool, used for control and power; love itself is explicitly rejected and cast aside as a tool that is no longer needed.
I used to think that a major component of western education (i myself call from eastern europe) was the emphasis put on critical thinking, on critical reading. The recent misreadings of Dune by the younger generations made me seriously question this assumption.