Because coin control is a complex way to achieve any given goal. It requires you to understand the transactional nature of the Bitcoin protocol. Fine for super-fans who don't mind studying, a bit of a pain for anyone who isn't. Look at how confused even some developers get about the relationships between addresses, balances and transactions.
So if coin control exists, what that means is people who aren't power users can't solve whatever problem the power users are solving with it. It'd be better to find solutions to the underlying problems, and then everyone can benefit. And often, I bet we can find fully automatic solutions, so it can be more convenient for power users too.
Making Bitcoin usable by everyone is an important goal, and thus so is understanding what people do with it. That's why I'm interested to know what people want coin control for. It's not a "I want to invade your privacy" thing, it's a "how can the software be better designed for everyone" thing.
Saying "I want to spend from a single address" is not a good explanation, by the way, it's just tautological. Why do you care about the precise outputs that are being spent? What is the high-level goal here? Is it to simplify your accounting? Is it part of some other scheme?
Actually coin control GUI would be an excellent teaching tool to help the beginning users and developers understand the Bitcoin protocol.
At the same time this is exactly why people who think like Mike Hearn oppose it: they oppose educating people about the inner working of the machinery. The key to control the people is to make them believe that they really need somebody more knowledgeable to ensure their safety.
Coin control is a beautiful example of anti-paternalistic stance and how it aggravates anyone who is a paternalist and wants to treat every user like a potential "grandma" or whatever else is the current polite word for "mentally deficient".
I think the Bitcoiner emancipation movement is getting formed here and now.