I've noticed this in a few things the last few years. The top and bottom of the shot are out of focus and it is super distracting to me. Maybe it is meant to draw the eye to the middle of the frame.
Yup, notice that as well. A blurry vignette. Needle sharp in the center, but objects that are the same distance are blurry at the edges of the frame. At first I thought they use vintage lenses, but it's probably done in post.
I sometimes do something similar on photos, where I darken the edges a bit.
Not necessarily, there are still lenses being produced today with vignetting, especially wide open.
Avoiding vignetting is a trade off between complexity, cost, weight, and other optical flaws. That said modern optical design and manufacturing has made it a lot easier to have nearly flawless (clinical) designs.
