Why are some DVD aspect ratios out of whack?

[St.ylo]

I just watched The Pink Panther, which is 2.35:1 Scope, and I noticed there was a small black line on the left, and a larger chunk of one on the right.

The Shield season one, which is supposed to be 1.78:1, aka filling a 16:9 screen, has a small black bar on the right and a larger one on the left.

I know some DVDs of TV shows have overscan areas for "garbage" that would get cut off on old TVs, but this seems different. Shows like X-Files and Community have tiiiny lines that change color with the background but they're easily ignorable.

Note that when I say black bars, they're nowhere NEAR the size of those you get with a 4:3 program; they're rather different. Different widths on each end and seem to be part of the different DVDs as they vary. Weirdly, they're not pixel-perfect, either. I swear one of the lines/bars had a slant to it, and on one movie, a small circular chunk of it was NOT black. I'm aware that DVD aren't as precise compared to 1:1 pixel Blurays, but I would have thought they could get the framing right.

I know I can put my TV on 16x9 mode, but zooming in like that will inevitably lose a bit of quality and a bit of vertical picture, however slight.