I've often thought that armors should be subdivided into "Soft" and "Hard" armor, to reflect that some is flexible and some is made with rigid plated over non-rigid portions of the human body.
Leather and Studded Leather would qualify as "soft" So would chain shirt, chain mail and scale.
Breastplate, Plate, Banded, Splint etc would be considered "hard".
On the original question: Not sure I agree. Having a hard surface to crush someone against has its advantages, and having a solid metal plate between you and the guy you're trying to pin does lend a certain confidence. I mean, you don't worry about him having a knife up his sleeve or anything like that.