Subtle is a cousin of beautiful.
Subtle design and messaging challenge the user to make her own connections instead of spelling out every detail. Connections we make are more powerful than connections made for us. If Amazon and Zappos had been called "reallybigbookstore.com" and "tonsofshoes.com" it might have made some early investors happy, but they would have built little of value.
Subtle details demonstrate power. Instead of being in an urgent hurry to yell about every feature or benefit, you demonstrate confidence by taking your time and allowing people to explore. They don't put huge banners on the Hermes store, announcing how good the silk is and how many famous people shop there…
And subtle messaging communicates insider status. I don't have to say, "Hey I was in Skull and Bones too! You should hire me!" Instead, a subtle (secret) handshake does all the talking that's needed.
It's tempting to turn the dial all the way to 11, the make everything just a bit louder. The opposite is precisely what you might need.
I'm aware of the oxymoronic nature of spelling out details about subtlety. At least I didn't explicitly point out the Spinal Tap reference.