IMO...people don't want things that look fake in a clumsy or unattractive way.  For example, hair that doesn't flow naturally in a reclining pose is just ugly and awkward, no way around it. But hair that is longer and thicker and glossier than real life...people generally do like that. 

SSS skin can look very realistic, but as has been noted...a lot of people are carrying it way beyond realism.  It's being used to give characters a flawless glow that looks almost airbrushed. 

I think what the average Poser user wants is "better than real."