There are TONS of websites that accept Bitcoin, and a growing number of brick and mortar stores accept it also.
You assert that black markets are the only factor that drive value in Cryptocurrencies, how about you back up that assertion with some evidence.
Close. You can pay for your motherboard in bitcoin, which is then converted to dollars and remitted to Newegg. Newegg eats the conversion costs as a transaction fee, and handles the transaction like any other dollar-denominated sale.
However, you aren't going to pay for your next motherboard with bitcoin. You're going to pay for web hosting for your drug sales or copyright infringement site with bitcoin, which is then sold for dollars by the shady web hosting company to people who want to buy drugs.
Just because Coinbase paid Newegg a marketing fee to run a bunch of promotions doesn't mean people execute everyday transactions in bitcoin. Bitcoin is still (statistically) only for criminal activity and speculation.