The misunderstanding has to do with limitations of perception and misunderstanding of what an aura is.
If I look at a tree, I can't see energy at the bottom of the tree - I know it's there because the tree would be dead, but I can't see it. If I look at the space between the top of the tree and sky then I can start to see the aura at the top of the tree or sometimes along the side of the tree. If I want to see a person's aura, i can't see it by staring at their body. If the person is against a particular background and the lighting conditions are right, then I can see some of the aura around the head and body.
Our eyesight is still limited. We know that energy is everywhere but it doesn't mean we can see it. Our eyesight is becoming more sensitive but it's still limited. For example, an angel or some other being could be standing right in front of you but because their energy is vibrating at a very fast rate, it's out of your range to see it. Energy moves and it's fast, that's one of the reasons it's hard to see. That holds true for the human aura or that of an animal, plant, or object. It's so fast, it's hard to see but if the conditions are just so - like the background is right and the lighting is right - you can catch a glimpse of it.
The second misunderstanding is what you think an aura should look like. What you are seeing are glimpses of energy which is why it's confusing. When someone looks at a person against a wall and relaxes their gaze, they will start to see something around the person - often it might look like a blue haze or white or yellow. They think they have seen the persons aura - what they've seen is just a glimpse of it but not the whole thing. Auras can be very wide and surround the body. Auras are usually more than one color and they can contain shapes. And as they are energy, they vibrate and are constantly in motion which is why it's hard to see the entire thing.
Even an empty room can have energy in, for example if your eyesight is sensitive enough to start seeing into other realities - they overlap with our reality so you could be seeing energy from another reality. You might be seeing hints of angels or other beings.
But the other thing that you need to remember is that there are also optical illusions which can create a problem. For example, if you have been looking at something that's red in color and then look away - you will see what's called, the after image which will be a shape that is green in color. The same is true if you look at something green and then look away - you'll see a floating red shape. This is also true for the colors blue and orange; yellow and purple. This is why when people learn to see auras, they are always told to take into account what the person is wearing because the colors can create that after image effect.
As to your comments about the blue streaks of light - this may be the way your brain is translating information about energy. You may be seeing other beings but your brain can't quite grasp this, so it presents this energy as blue streaks. You have to understand that what you see isn't what's actually in front of you. We see with our brains. Take for example the angel standing in front of you; the brain can't yet wrap it's head around that concept so it might present you with some image of bits of light. It's not just that the brain can't fully translate the fast moving energy, it's also that it can't grasp that reality. People have spirit guides and angels all around them, but most can't see them. Not just because the energy is moving too fast but because our brains just can't compute that type of information - yet.
Since you're very interested in the subject of auras, it might be helpful to start reading books on the topic. I think if you start to read up on the subject and learn more about it; you'll be able to get a better understanding of what you're looking at and how our eyes work in perceiving the energy.