Actually, they are arranged (somewhat) in order of frequency.
A, B, C, D, and E are among the most common letters in the language--E being the most common.
V, W, X, Y, and Z are much less frequent.
There are plenty of exceptions, like S and T--despite being common--are towards the end of the alphabet.
It may just be a coincidence, though. I looked up the history of alphabetical order, and no one seems sure about it.