Majik, Majick, Magik, and all other odd spellings are not words! They are a means of "looking cool" (though I've never known how mispellings on purpose are a cool thing), and they're a means of accomplishing goal number one below.
So, why do we spell "magic" like "magick"? Well, we're often given a few different reasons:
1. Because we need to differentiate between stage magic and our type of real witchcraft
Now, is it just me or has no one ever had a problem with this...ever? If you do, is it simply impossible to clarify with "No, I take part in the religious practice of witchcraft"? A differentiated spelling isn't necessary. In addition, we have several homonyms in the English language (or even words that have complete different meanings depending on context), so why do we need to change this word to make it different?
2. Because Crowley told us to spell it that way
I know a lot of Wicca is based on the teachings from the Golden Dawn and Crowley's writings, but since when is he the end-all-be-all of Wiccan teachers? (The reason I say "Wiccan" is because it is mainly Neo-Wiccans that you find clinging to the differentiated spellings of "magic".) Just for reference, Gerald Gardner used "magic" in his works. So, why do some Neo-Wiccans ignore him and go straight to Crowley?
Let's examine why Crowley insisted on spelling it this way and see if it still makes sense. Shall we?
In addition to differentiating from stage magic, Crowley's reasoning was as follows (from Wicca for the Rest of Us -http://wicca.timerift.net/magic.shtml):
"Conversely, Crowley also gave reasons why he changed the word by adding a "K" such as the mystical significance of the number 6 (the number of letters in "magick") and 11 ("K" is the 11th letter of the alphabet). He also gave a distinct definition of what "magick" meant: "the Science and Art of causing Change to occur in conformity with Will". Will here is True Will - basically your higher and ultimate purpose in life. Hence, casting a spell to get Bobby to date you or a higher allowance would not be magick. So, when people use "magick" in this capacity, it makes sense. Interchanging it indiscriminately with magic, however, is silly."
I quite agree with the above. I don't use "magick" even in this context, but I would be willing to accept it used under these guidelines. However, as it said, not all magical workings would then qualify as "magick". In fact, "magick" would probably be quite advanced as it involves so much introspection.
3. Because "magick" was how it was once spelled
So? Do you spell everything in your life (or even your magical practice) how it was spelled in the days of yore? That must be quite exhausting and you must be quite the language scholar! I've never understood this reasoning. Sure, some people really do use Old English in ritual, but do they then keep running around speaking like that when referring to it? Probably not. I'llstand by their right to use it in ritual if it feels comfortable to them (though even as a trained Shakespearean actor, I find it sometimes troublesome), but that doesn't mean it has to transfer into every day life when discussing religion and religious practices.
So, the "k" can be used in some circumstances, but they are few and far between. Other than that, why do you guys think the magical community (particularly the Neo-Wiccan community) is sticking with this "k"? Do you use the "k"? If so, why?