The curves existed long before digital video and computer graphics.
Because in the age of analog signal processing you'd compress noise into the contrast area least noticable and provide more gain in the area well covered. Analog vs. Digital is a red herring, and doesn't change the nature of the mechanism, and why it was used. It's a workaround for technical limitations todo with signal frequency, no matter if you have it in the analog or digital domain. Todays displays and sensors rival and surpass the eyes capacity for contrast in many use-cases (obviously not all, since we also have low-light rods, and dynamic chemical response, but that's another topic).
I think it needs to be made clear. The displays purpose is to represent content as authored, nothing less, nothing more. If for technical limitations you have a compression in the display device, that's unfortunate, and not something to be cherished. Your display isn't your video editor, it isn't your director, it isn't your cameraman, and it isn't after-effects. That's not its purpose.