When wigs were introduced, judicial wigs had a small version of the skullcap and coif sewn into them. Law students, not yet entitled to wear wigs, continued to wear the legal skullcap for some time after the introduction of wigs, but by the early eighteenth century, it had disappeared completely. Much writing in this area tends to confuse the legal skullcap with the coif. In short, English judges and barristers began wearing wigs and robes because everybody in polite society was wearing wigs and robes in those days. They continue to wear them because nobody has ever told them to stop.
Wigs are expensive, and English judges get a stipend to cover the cost of their wigs and robes.
Barristers, on the other hand, must buy their own, and there is a thriving market in used wigs. It is not clear, however, that used wigs are cheaper than new ones. Tradition being what it is in Great Britain, wigs that have previously been worn by great jurists and lions of the bar acquire a certain cachet that makes them highly sought after. It is also not unheard of for wigs to be stolen and resold on the black market. In April 1992, there was much speculation that English judges might finally stop wearing all their ridiculous paraphernalia and slip into something a little more comfortable.