Why did they decide iksar couldn't wear plate?

[DrKvothe]

They probably over-valued the innate AC bonus, thinking that being able to break the AC cap that other races are limited to would make it the must play race for warriors. This is sort of ironic since the size (easy to target) and FSI of ogres are arguably more important. Giving iksars a huge penalty with some lore behind it let them feel balanced giving the AC bonus.

IMO it's super dumb. Yes, iksars have scales...They also have TEETH and a TAIL. Why not do something with that, like a racial attack bonus that's easily offset by adjustments to starting strength.

It's pretty similar silly restriction to some of the class specific weapon restrictions, intended for balance but unrealistic. Monks can't learn to use slashing/piercing weapons? Dude can do a flying kick and a dragon punch but can't figure out how to use the dagger* that wizards start with?