There's a point to everything, whether the point is significant or trivial. The point of fanon or head canon is to fill in the gaps of what hasn't been explained by the series, either because they haven't gotten that far in the story, left it ambiguous on purpose, or in a lot of cases, error on their part in the form of plot holes or other inconsistencies.
I myself have flexible headcanon. Sure, I'll come up with an interesting idea to explain a plot hole, but I'll never talk to someone else as if it's a known fact that they need to accept. I'll have a number of ideas about how one character might respond to a situation, such as Spike being feminine or masculine in his methods. But through past experience, I've found the more I try to set in stone, the more frustrated I get when others don't see it my way, or the writers come up with something that contradicts it because those damn fools are too ignorant to recognize my genius for what it is
One of my favorite fan ideas is that Starswilrl the Bearded is a great ancestor of the Great and Powerful Trixie, and that she's the disappointment of the lineage. There's no real evidence to prove that, but there's also nothing to throw it out either. It's fun to think about, and it creates some interesting scenarios for art or stories to delve into that idea. If an episode comes along to ruin that, I'll be annoyed for the afternoon, and then I'll move past it. No biggie.