No, SD, is not necessary for great sex (this coming from one who has played for both teams), However, it is so important. Not because that we all can't have a good time without an erect penis, but I think men ( I am only guessing) tie so much of their self worth to their penises. You just have to look in all that junk email we get about penis enlargement and enhancing and see that there all whole industries dedicated to them.

I think that whole performance anxiety sets in and we begin the whole cycle that is so hard to break.

So, for me ( because I only know about me), when my husband could not get an erection or worse yet, lose the erection right before intercourse, I felt that there was something so ugly about me. It made me feel so unwomanly. I felt the way you might feel if every time you were making love to your partner, she suddenly got the urge to vomit.

Now we all know feelings aren't facts. But those are the feelings elicited.

Arguing with reality is like trying to teach a cat to bark—hopeless. (Byron Katie)