Excellent question! Thank you 🙂
Well first, off unfortunately for you (and most of witches) you have been given the wrong idea about what is traditional and what isn’t. Casting circles is a ceremonial magic practice. Its true, witches do work with the geometrical shape of circles throughout, and the ceremonial circle is essential to some forms of witchcraft, especially wiccan witchcraft. However, it is not central to most forms of traditional witchcraft, which do tend to work with directions and shapes, but do not generally use the container defensive format of the (outer circle) wiccan circle.
We must start with what is the circle casting and its purpose. The circle casting is a sphere that contains energy to be released as a cone to some purpose (as decided by the coven or witches ahead of time) and to keep out dangerous spirits. In ceremonial magic the circle is to protect the sorcerer while they summon a demon to command into a nearby triangle. Some traditional witches do either, but many do another kind of working with space for certain kinds of ritual or don’t make any such action.
A few “circles” known in streams of traditional witchcraft (a variety of other kinds of witchcraft in existence prior to and contemporaneous to the public revelation of wicca) and reconstructed forms of witchcraft based on folklore and historical records are as follows:
The cross roads. Many witches work at the crossroads where three or four roads meet and work their magic there. Its a kind of acknowledgement that a witch owns her own fate and is her own god by admitting that she is the center of the universe where the directions or the parts of the world meet (north east west south or land sea and sky).
Treading the mill. Some traditions of witches circle not to protect, but to enter a special trance state. They look over their left shoulder and chant at an increasing tempo while pacing steadily round the circle. They descend into an underworld location and interact with the gods or spirits there.
These types forms are used by some kinds of traditional witches, but they are not the wiccan nor ceremonial circle. Yet, just as often traditional and non traditional witches do nothing of the sort at all. The just get to it and do their witchcraft wherever. Be it in their kitchen, the woods, their office, the bedroom, etc. The whole thing of casting a circle is often more of a spiritual thing, whereas doing some witchcraft is just a thing of the moment, do a spell to get a result. If you aren’t getting into a sacred space for spiritual workings you don’t need to do the whole circle casting. Most magic doesn’t call on spirits or energies outside the witch and the materials directly in front of him so there isn’t a need for him to worry about the whole spiritual world.
As for pagans who don’t have altars. Well I think most don’t. I personally love altars, I have four in my bedroom alone. I really get a lot out of them. But they are just a focus. The world around us is alive with spirit. I am an animist personally, but most pagans see gods and spirit and fairies and other soulful life all around them. A surface of decorations that create a focus and a special home for dedicated workings is really a huge help and adds something I can’t put into words. But it isn’t a requirement when really the whole world is alive and not all pagans are devoted to regular work with specific spirits, gods or fairies. A lot of pagans and witches just make whatever surface they are near suitable for doing their witchcraft or when they are doing magic or dealing with spirits, gods and fairies into a temporary altar if that’s what the project calls for.
I really rambled on there!!! Well if you have any follow up questions please send them.