It's definitely the smarter alternative, but in a world where PayPal is the king of E-commerce (Due to its links with eBay and actual resolution centre), most people will continue to use it. When I joined Sythe it was the only method I knew of, so obviously it was all I took. Unless Bitcoin really does become the main payment provider on the internet, which I highly doubt it could, then only accepting bitcoin would severely damage your business.
It also doesn't help that people seem to think bitcoin is very hard to learn, when it's really relatively easy.