As the child of deaf people, I have an appreciation for closed captioning that may be greater than the average person. Therefore, it drives me nuts when I see captions that's not on a suitably contrastable background.
I'm used to black blocks with white text, because that's what I grew up with in the '80s, but I'll accept any color combination that has suitable readability. I've even seen turquoise or pink on a black background, and it works great.
Granted, the black background can be a hassle when it's overlaying news captions. That's unfortunate.
So when I see a TV that shows white/gray text with no background, I just want to rage.