It's hard to think how sex was used to sell scifi in the middle of the last century. To some authors it must have been an acutely embarrassing moment in their life as they look back on it.
Much literature follows the themes of love, sex, revenge and death but you do tend to think that scifi is apart from it, more boys own material in many ways, so it is accessible by all readers, including the young.
Most of the cosplaying you see is not meant to be titillating but unfortunately so in many cases. Levels of depravity and innuendo only evident by mistake