Which red? There isn't a single, true "red". And different materials produce different reds (my work's Sony BVM-X300's reddest red is going to look way different than your monitor's red). Not all displays use only RGB color primaries, too. For example, at Dolby's office in San Francisco they have a projector in their theater that uses 5 (IIRC) color primaries, not 3. 6-primary projectors exist. And other non-RGB displays.
> When I say (255, 255, 255), I expect the display to show me something as close to white as possible
Which white? D50? D55? D60? D65? D67? Something else? And yes, these different white points (and many others) are actually used in practice.
> (and at the brightest possible setting).
100 nits looks way, way different than 4,000 nits. Some monitors can do 10,000 nits.
> When I say (0, 0, 0), I expect the display to show me something that looks as close to black as possible. It's up to the display technology to decide whether this means just turn off that pixel on the screen or disengage the backlight or do whatever, but at the end of the day it's just trying to approximate black.
Which black? This might sound dumb, because we can agree that there is an objective "absolute black" (i.e. zero photons). But when an artist creates an image, the monitor they use has some version of black. If you don't account for that, the image may be distorted. Blacks can be crushed, for example.
An absolute color space exists. It's called XYZ. We could use it. Some image formats support it.