Oh, goodness, no. It might be uncomfortable, or not my style, or impractical for my lifestyle. I might feel too self-conscious in it. Maybe it's just a color I hate. Or maybe I have poison eye for the style. Or it might not go with anything else in my closet. Many reasons.
Oh, and it definitely depends on whose opinion I am asking. My husband might have ulterior motives for liking something.
A non-fashion friend might not be particularly critical, or might not want to offend me. My mom has totally different taste than I do. I have to say I trust you guys more than most when it comes to telling me whether or not something looks good.
I probably wouldn't bother to show it to you guys in most of those cases though. I do occasionally ask about things that I am confused about how to style or whether it works with my wardrobe. (Case in point: the VC midi skirt, current source of much pearshape angst.)