It's just not how it works. As long as the assumption is that the material the armor was made of is more durable than even the flesh and skin of the troll, it makes sense to them to wear it.
I'm not saying you are wrong to feel that way. I'm just saying that's not the only way to look at it. You say it doesn't make any sense that a bad ass troll gets no benefit from armor, I say it makes sense to me; we'll get nowhere that way, which is where this whole thread has been going for 2 or 3 pages. You and I don't agree on the basic premise, I think, of your argument; that somehow armor and cyber and magic and whatever all have to scale up in the same way and all be additive in some fashion without diminishing returns. I don't think that is necessary mechanically, nor do I think it is necessary fictionally. Maybe in some kind of "real world" it might be true, but I don't actually want much real-world in my Shadowrun; that is often as much distraction as it is useful.
I like my games to at least feel "realistic" on the surface, meaning they have to make sense from a common sense perspective at a cursory glance. If not, that's breakig my suspension of disbelief and immersion into the game world. I'm not into systems, which are going for "rule of cool" and "genre emulation" over at least a baseline attempt on a cohesive realism. IRL, people put as much armor on themselves, or vehicles and such as they could get away with, in the appropriate context and goal.
Moreover, I don't see SR characters that extremely. That is much more anime/comics level. Sure Superman doesn't need armor, because he's already invulnerable (except, when he's going against a foe knowingly using cryptonite, in which case, he 'does' put on armor...). SR characters aren't Superman, even trolls. For them, putting on as much armor as they could in a given situation is the sensible approach.
Also, this discussion of whether and how armor should matter seems to be missing the elephant in the room. To my mind, almost everything that the AR/DR system achieves practically in the game could have been achieved with a simple trait comparison system and almost no math at all. I mean, in the end, there are a heck of a lot of numbers in the rulebook that you do some math on (man I dislike that -4 difference) to hand out a single point of Edge. This stands out in comparison to the other two potential sources of Edge which are almost entirely decided by GM Fiat. Why is this one bit so complicated compared to the others? If the goal was to be simple, it fails; there are still all kinds of one off modifiers throughout the book that you have to keep track of. If the goal was to be easy to implement at the table, it fails; there are too many cases where you'll have to remember some situational change which might make the difference between Edge or not. If the goal was to still allow for discriminating between all the different weapons and armor, it fails; it just ends up handing out the same point of Edge.
Agree with that.
So what was the goal of it?
Having to do less math on the fly, I guess. I'd agree, the edge system is not particularly good at being really easy to use and learn, not like adv/disadv in D&D 5e. In some respects, it's actually harder, with more rules to keep in mind and more potential analysis paralisis. On the other hand, it's more interactive and maybe more "fun" than calculating modifiers. I can imagine a version, where I'd like it, but as it is now, I'm not quite sold on the whole.
If you want something that makes no sense to me, there you have it.
But even that, hey, that's just my aesthetic preference, really. I like games that have streamlined, concise, and elegant mechanics; SR 6E is not that and it won't be. But it IS Shadowrun, which I need very badly in my life right now, so I'm going to play it, make do, and enjoy it where I can, which I suspect will be a lot after two sessions so far.
Have fun!

I think I'd wait for a few supplements and see how it shakes out. Right now, our group is deep in a D&D 3.5 campaign and we have an ongoing SR campaign at rest which started with 3e and switched to 5e.