Short answer: It's just plain inaccurate. If you happen to look like your season's stereotype, or like my daughter you have an amazingly intuitive sense of your best colors, maybe you get lucky. You pick a season (maybe based on some kind of ad hoc method) and you look great in it. But for most people, that's just not how it works.
Long answer: I took a chance on a handbag from ThredUP recently. (Great source for like-new clothing at reasonable prices, by the way!) In the photo, it looked like a rich Dark Autumn burgundy. In person, it was True Winter fuchsia.
That's pretty much how online analysis works, even if you're asking trained analysts. If you're asking Facebook, you're up a creek without a paddle.
In a series of photos taken on the same day, in the same lighting, with the same camera, in the same "neutral" outfit (just because you're wearing grey doesn't mean it's neutral grey) there will be variations in the appearance of your skin tone. How do we know how you really look, if we've only ever seen a photo? How do we know the True Winter green you're self-draping with is really True Winter? Unless you've harmonized it to all of the fans, we don't. And even if you have, and you've harmonized a green to every season, it's just not enough. Comparing a green from every season might tell you something, but it won't tell you everything. If you've had an in-person analysis, you know how many steps go into determining a person's season. Everything is checked and re-checked in a grey room with full-spectrum lighting.
Determining your season based on lipstick draping is another issue entirely. The first, and it's a big one, is that not every person of the same season will wear the same lipstick colors. One Soft Autumn's Holy Grail might be another Soft Autumn's Death Warmed Over. The second is that, like clothing, we can't interpret lipstick in isolation. In photos, how do we know what we're really seeing? How do we know which lipsticked version of you is the real you? As an analyst, even if I had someone in my studio trying on a lipstick from every season, I would never even hazard a guess.
Asking for opinions from internet friends is folly, because (and this sounds exceptionally rude in print, but I promise I'm not being snarky) most people just don't have any clue what they're talking about. Leaving aside the issues of photographic inaccuracy, people respond to the colors they like, colors they think fit your personality, colors they're familiar with seeing you in, colors that deliver drama but not harmony. It's not conscious. We all do it. I do it!
Even in person, I couldn't determine a person's season without draping. When I see a client in neutral-grey, I make a guess in my head, then set aside it aside and see where the drapes take us. Sometimes I'm right. Usually, I'm not. That's the beauty of the drapes. If you interpret them correctly, without shortcuts, without bias, they never lie. They're like the sunrise.