I think sometimes people aren't told the negative and then they are shocked after birth. Both sides is probably better as it's more realistic.
An example is my cousin just had her first baby (she's 39). I don't think anyone said anything except the positive and she is still shocked at the pain 2 months later. She was disappointed from her perspective that no one was absolutely truthful.
I think the best thing to do is research all you can, all sides of birth, and then you can go into it with an open mind. Every experience is different and I think people just want validation as to what they went through. I don't believe they're really telling you what is going to happen, but more what happened to them and therefore that is their truth. If they didn't get the perfect birth they may have wanted, then they might find it difficult to see someone else get it? xoxoxo