Don't Wiccans practice naked?

Some do and some don't. The term we use is "skyclad", and it's not a universal practice among witches or Wiccans. Some Wiccans who are solitary go unclothed when doing rituals, and covens may also do the same. But that doesn't make us nudists. It is not a requirement that you be naked during rituals or any other gatherings just because you are Wiccan. It may be a requirement of a particular coven, though

There are several reasons why nudity might be desired during rituals:

• Clothing blocks energy (according to some people)
• Being nude represents the deep trust between coven members
• Lack of robes removes all indications of rank, and therefore places all members as equals
• Shows the level of commitment to the Craft and one's coven

Nudity is usually restricted to formal rituals, rather than being a part of everyday Wiccan life.