If you want a reason for spikey pauldrons... to catch blades maybe? Like how some swords and polearms have hooks to "capture" a blade.
Granted you wouldn't want a blade to be captured next to your head... hey i never said i was an expert.
I always thought that the bolts on pauldrons or bangles were for added offensive capabilities.
The normal protective pad on the shoulders and lower forearm would be for protection if you couldn't avoid an attack and needed to take a hit, so basically a "better something than nothing" strategy where you take the hit on the pauldron or the bangle: a contingency move which takes less precedence than a dodge or a parry.
But at the same time if you were to hit someone with these layers, it would still do some damage (it is made up of presumably hard/harder stuff). But since these paddings are relatively smooth, pressure point(s) would be low: so damage, minimal. This is just like when a wrestler (I'm trying to keep theme since this is GB and they talk about wrestling quite frequently here) hits someone with the flatter side of a steel chair as opposed to the edges since slamming the edges of a steel chair onto someone at a good speed would really mess up their day.
So say you are in a fight and were equiped with Cloud's loadout, if the Buster sword was currently engaged (you just sliced some monster and it's a heavy sword) but you needed to attend to the other things coming at you with ill-intent, you could show them pain either by shoulder bashing them or back-handing them. And the bolts would presumably damage them more, and cause them to have deep breaths of pain (pssshhh... ahhh... pssshhh... ahhh...).
I suppose a better analogy than the steel chair would be a lego brick? Imagine walking to the bathroom in the dark at 3am, and you accidentally stepped on a relatively smooth and flat pauldron: you curse because the pauldron may be slightly dented out of shape now, and your foot feels slight discomfort. Now imagine the same, but you step on a pauldron with several lego bricks welded on there: you'd be dead.
Sorry for the long post, and I hope I didn't come across as condescending (definitely not the intention). I just always think about these things (have been told by others that I am an "over-thinker"), especially recently coming from replaying Dragon's Dogma on steam and asking myself about why certain armours look the way they do.
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