You do not understand Slaanesh but that's okay because no one does. Slaanesh is not the god of tits and boners. Nor are they the god of sex, drugs, and rock and roll. Slaanesh is the god of all sensation, all desire, and the excess of them both. Sex is only a small part of their domain. Every time you have felt desire of any kind, you have felt Slaanesh. The feel of silk, the taste of rich food, the smell of perfume, the sight of beauty, the sound of music. Slaanesh has no need to lure in converts, you were a slave to their will from the moment of your first breath.