Because cultural differences and biases in perception are a real concern. Just to give a small example, a friend of mine, from japan, once wore to a conference

Because cultural differences and biases in perception are a real concern. Just to give a small example, a friend of mine, from japan, once wore to a conference in the USA (quite innocently) a red armband, as is commonly used over there to mark group leadership. The result were accusations of her being a nazi sympathizer due to lack of knowledge of that custom.