It seems the favourite place where buying socks it is the department store. The high quality underwear shops quite disappeared during the years and the indipendent clothing stores are paying to the socks only little attention. More and more people buy socks on the web. The offer quite increased during last couple of years.
It is depending on the Country too. In Italy 80% of the people still buy socks on the market place, but of course this is concerning the medium/low quality segment.
Usual the problem of department stores it is they are buying brands only and small Companies producing high quality have hard time in finding place there.
The web gave more options to the final consumer, but since it is not possible to "touch" the quality, people has to trust the brand and so it is extemly important for a Company to build a strong quality image.