I wonder if Wicca specifically is more rigidly structured, as in adhering to festivals on definite and specific days/dates in the calendar - Owly might chip in here when he catches up with the thread.
In Wicca (capitalised) every festival and every full moon has its attendant ritual set in stone by GBG! No High Priestess of lineage would dare to amend even one syllable in case it were brought to GBG's attention, or one of his multiplicity of deputies.
A verbal reprimand in front of a meeting of every High Priestess would be the result and a note of the reprimand woud be entered into the Coven's Book of Shadow's and would have to be hand-copied into the BoS of every Covener. As you will imagine there were very very few deviations from GBG's and Doreen's scripts.
The reason for this was GBG's membership of the Freemason's and a large part of Gardnerian Wicca's rules and rituals were based upon the rules and rituals of Freemasonry.
There still exists an official attached to the highest level of Gardnerian Wicca who is responsible for investigating any, even the most minor, reported breaches of these rules and to my sorrow I know personally of two Third Degree (the highest) High Priests who have been declared Warlock (oathbreaker/traitor) and are treated by Gardnerian Wiccans as if they do not exist and will be treated so unto death.
Most wiccan Covens (uncapitalised) write and perform their own rituals; Hedgewitches, like the Lady Rhi, do whatever they feel to be appropriate to their own particular path (as described in the Lady Rhi's post above).
