Well, the idea of using unfinished concrete (the origin of the movement's name) was something of a modern/internationalist reaction to the earlier excesses of nouveau and deco really. It wasn't that concrete is a superior material for structure, the ancients knew that. A better current example (that argues the opposite to your point unfortunately!) of form following function is cheap [edit: cheap isn't what I meant, more 'the cheapest available using today's sophisticated engineering', which obviously isn't cheap but real estate doesn't have that reputation anyway] curtain walls in high rises. Pretty insipid but people love it; there's no accounting for taste, especially among those who have no appreciation for the finer things.