Why do Goths wear black?

Wearing Black has been the hallmark of the coffee drinking intelligentsia for nearly 400 years. Back during the early Renaissance the rich (and therefore educated) were dressing in flamboyant clothes made with expensive coloured dyes and gold and silver decorations. In the early part of the 17th century as the Renaissance was spreading into Northern Europe the Dutch invented the first permanent black dyes. At the same time the Dutch were surpassing the Italians as Europe's premiere merchants and Amsterdam was becoming the centre of power and learning for Europe. Dutch merchants also introduced coffee and chocolate to Europe around this same time, ergo you suddenly had the wealthy and educated merchant crowd and the artists they supported sitting around in coffee-houses all dressed in black, drinking coffee and eating chocolate for a buzz. Bach (who used to spend a lot of time hanging out in cafés, jamming with his contemporaries) even wrote a "Coffee Cantata" about a woman who wanted to drink coffee despite her father's wishes and the mores of the time.
While styles changed amongst the rich and powerful the style and image of the black-clad artist and intellectual persisted. The style persisted through the early-to-mid 19th century Romantics on into the late 19th / early 20th century Avant Garde artists. The Weimar intellectuals such as the founders of the Bauhaus school also continued the tradition leading directly into the Beat Generation followed by the Situationists, punks and eventually Goths.