So, more broadly, why do raw files require significant tone curving to look "right"? In Camera Neutral, for instance, they seem flat and lacking contrast. But again -- I should be seeing raw sensor data with basically just a gamma correction, and the sensor and I are seeing the same photons, so I expect roughly the same result.
I'm arriving late to this party, but it seems to me one point missing from the responses to date—I think Andrew implied it, but I don't believe he stated it explicitly—is that until you change the defaults, Lightroom is configured to display colors and tones in a normalized fashion that renders them similarly for all camera manufacturers and models.
“If you fell in love with the way your image looked when you chimped the LCD on the back of the camera, this first look in Lightroom or Camera Raw might be disappointing. Neither Lightroom nor Camera Raw uses the camera-maker’s software development kit (SDK) for rendering the digital negative, so expecting the preview to look like the camera LCD is unreasonable. When he was designing the rendering engine, Thomas Knoll made a conscious decision not to try to match the camera companies’ ‘looks,’ but instead to present you with a reasonable and normalized preview of your image.”
Jeff Schewe: The Digital Negative: Raw Image Processing in Lightroom, Camera Raw, and Photoshop, second edition
Whenever you select a different profile (in the Basic panel of the Development module), you get different colors and tones. Adobe provides its own set of standard profiles (these are the normalized ones), some monochromatic and "artistic" variants that more radically alter the default renderings, and a set that attempts to imitate the JPEG processing options offered by each camera; these last camera-specific ones vary in quality, in my experience—based, I suspect, on (1) how much assistance the manufacturer provided to Adobe and (2) how much personal experience the Adobe software developers had with a particular camera. The initial position of the sliders doesn't change when you select a different profile, so from the starting point provided by each profile you have the full range of adjustments.
With respect solely to the tone curve, Lightroom offers an
Auto setting, again in the Basic panel of the Development module, that works surprisingly well for many images. This feature recently was updated by using machine learning (presumably "neural-network" technology) to mimic the way experts in post-processing adjusted the tones in various samples of photographs. Like the profiles, this can be used as-is, or as a starting point for further adjustments. Unlike the profiles, this tool
does alter the sliders, so you can see precisely what it has done to achieve the effect it produces. When I'm having difficulty getting the global tones I want from a particular image, I find that the
Auto tool's magic incantation sometimes helps me figure out where I've gone wrong. (Of course, in many cases difficult images will become more tractable if you apply local in addition to global adjustments.)
Long story short, if you don't like the Adobe profiles, don't use them. If you don't like how Adobe has profiled your particular camera(s), roll your own: there are plenty of online tutorials on how to do so. But with a little practice, it's always possible to get where you want to be no matter where you start.
With respect to the intellectual exercise of understanding the precise semantics of the Adobe profiles, or how its development staff arrived at the settings for specific cameras, I guess you'd have to ask the Lightroom and Camera Raw developers. Good luck with that.