Is the real world a storytelling game about creating drama for people's entertainment? No. Why then are we even asking this?
But, this is basically what you are doing.
If I play a dwarven druid who comes from a long line of armor-smiths, then even if you never put me in a scenario where I have to choose between wearing armor or not, you have already told me that my character believes in the taboo of not wearing armor more than he believes in his family's traditions. Or you are telling me I can't make that character.
No matter how you slice it, even without a Sophie's Choice you have stepped in and said "this is what your character believes, and this is a belief that they will hold onto with no compromise and no question."
Do you just not read more than three words of anything I post?
My point wasn't that "no one can believe it is important" my point was:
WHY CAN'T MAKING IT IMPORTANT BE MY CHOICE
What? Becuase you think it is important no one can ever decide it isn't? All people must obey your beliefs? Obviously not, that's ridiculous, and yet that is what you are saying. That I can never decide what my character values more. I must always decide that this taboo is the most important belief they have. And that is BS
Edit: Just to take a moment to highlight something. Which is the more engaged player?
Why doesn't your druid wear metal armor?
Player A: "I don't know, the rules said they don't. I'm just doing what the book tells me."
Player B: "Well, the rules don't require it, but it is a tradition for druids. So, I started thinking about how I could make it make sense for them to swear off armor. I decided that there was a mining town near where he was trained, and they stripped the forest to mine and make charcoal to armor some lord's army. So, the association with the people who destroyed his homeland pushes him to avoid using any metal, even coins, as much as possible."
If people want the tradition and taboo to matter. That's great. More power to them. But forcing all of us to follow beliefs we don't agree with? Pointless.