I have yet to see a quilt that was so heavily quilted the piecing is lost. I am a huge fan of the likes of Judy Madsen of Green Fairy, Renae Haddadin, Sharon Schambers and Karen McTavish. All of them quilt pretty densely. The photos of heavily quilted quilts I have seen as well as quilts displayed in shows compliment the piecing and are gorgeous IMHO. As you are not allowed to touch show quilts I don't see how you can make a determination that it isn't soft and cozy. You definitely can't tell by a photo is something is soft and cozy. A friend of mine recently quilted a NYB quilt very densely and because she used wool batting it was very soft and drapable and there was not as much a 1" x 2" spot on that quilt that wasn't quilted.
Art quilts or thread painting are different, as they are just that, art quilts and not meant to be functional other than works of art to hang on a wall. However, I have attended a trunk show of an art quilter who did a lot of thread painting and heavy quilting and again, because she used wool batting, these quilts still had some amount of drape but they were not meant to drape, they were meant to hand on a wall like a painting.
Would it be possible for you to post links to pictures of quilts you have seen that the piecing is lost due to quilting? I am very curious to see what prompted this topic.