The two events both choose a bank holiday, presumably as a significant proportion of their intended target audience see a 3-day weekend as better than a 2-day. Given that a good number of those attending will be campers that doesn't offer many likely dates in the year. This is the more so when you rule out August because the Whitby FF runs right up to it.

Yes, Hutton-le-Hole and Whitby are quite close together, but comparing the two programmes suggests to me that each event is catering to its own distinct group, and that the number of people who would wish to attend both (but be unable) is relatively small. Do the organisers (as opposed to their vocal champions) of either event feel that they have lost out because of the proximity of the other? If not then this would seem to me to be a needless debate.