It's the vintage lenses that first introduced the flare. Light intensifies in one section of the image and causing shapes and light diffraction that, back in the old days, were un-usable and discarded. Today it's something many filmmakers strive to add to the look they're going for.
It's either captured in camera or added in post. According to the video it gives a sense of rebelliousness and being rogue and shooting without rules, but for me, it puts the viewer in the head of the person filming the event or story too. It gives the person an idea of what it must be like to experience the sight and therefore makes it more real too.
It is easier to get lens flares in older lenses. Today the lenses are coated to remove the risk of getting flares. The shape of the lens flare depends on the lens aperture and amount of blades that create the aperture, although you can add these in post or on your iPhone after you've taken the shot. In my opinion, best lens flare app for iPhone is the Lens Distortions app. They also make a Lens Distortion tools for the desktop to be used in Lightroom and Photoshop.
Do you use lens flares in your footage or still photography? Do you think it's a trend that'll come and go or something that's part of photography and image making?