Sex, or Plot? The eternal question. Sort of like, Why did the chicken cross the road?
e.e.norcod (nice s/n btw, and is the cod part anything like a cod piece?) offers the most salient view on the thread's question, i.e., visually oriented can view much elsewhere.

At bdsmlibrary.com, it is up to the reader to use his/her imagination in hopes of following whatever the writer offers in their submission.

Personally, the use of character and plot richly enhance whatever fictional sex might be portrayed and hopefully that also engages the reader. Sometime this tact works, other times it does not. But hey! What was it that Lincoln used to say on the subject of relating to others?