As for anonymity and fungibility: I believe tumbling services are good enough today, which is why buying on a dark market works. However, it is not perfect and this is why projects like Monero, ZCash, MimbleWimble, TumbleBit and Xim are important.
This isn't the most accurate thing, but looks to me like several millions USD worth of volume just in Bitpay. That doesn't account for all of the other payment processors, or the peer to peer payments, or the exchange trading, etc. I'm not saying dark markets aren't an early driver of Bitcoin, but it's not where the majority of the action is now at all.
Exchange trading is not really using bitcoin, it is buying/selling bitcoin. This is like saying buying a car is an application of cars...
Having said that, Bitpay is processing more than I thought. The data in that article would mean it's about $5M per day... I'd love to see a breakdown of this to figure out why people are spending bitcoin for everyday things if it'd be better for them to just use a credit card (to get rewards, to not have to hold a volatile currency, for consumer protection, for faster payments, etc.)
That and you can buy cash-like goods like gold bars which would be prohibitively expensive or impossible to purchase via credit card.