Okay, let's see.
First off: "Bypassing the armor by hitting weak spots." Have you ever tried this in real life? As in, really tried it against someone with a shield? The precision required is nearly superhuman, and even if you do have the accuracy for it, getting in on someone with a shield is extremely difficult. I'm not saying it's impossible, but the point is, while you're trying to do that, you've got an angry guy with a shield and sword in a very good position to **** you up as you try and stab him through his guard.
I'll concede about the 'real combat' usage, bad term on my part. Fair enough.
Shields make much better weapons than you give them credit for. Keep in mind that they were built for deflection and ease of use, and that you can easily smash someone's hand with a shield. Furthermore, the short reach is negated against a dual wielder, because a shield has similar range to that of a blade short enough to dual-wield [which is approximately between twenty to twenty-eight centimeters].
As for the metal and wood, do you just not know much about Japan? They used bamboo for their woodcraft, which while strong for bows and spears, isn't suitable for shieldwork. As for metal, it's pretty widely known that Japan, due to being an isolated island nation, had limited resources. Why do you think the common soldier used a spear instead of a sword? Because spears only required a small biit of metal and a shaft of bamboo. Swords of all kinds were the privilege of those who could afford them, and the steel that Japan did have was weak and low quality - that's why katanas were made by folding steel, the folding process was to reinforce the brittle metal.
To be fair the sword is a romanticized weapon period. The spear has always been the favored weapon on the battle field due to how well it works in both formations and even one on one fights. A lot of people think "You just need to get in against someone with a spear" but in reality that isn't easy against someone knowledgeable in it's use.