When you manipulate the tone curve of an image so that both the darkest shadow detail and the brightest highlight detail from a 14-bit RAW file that uses the full dynamic range available is visible at the same time on an 8-bit monitor it tends to "flatten" the image a little. Techniques such as HDR, Exposure fusion, using layers to set different exposure levels for various areas of an image are an attempt to increase local contrast in the image so that it still has some "pop" while preserving the detail in both the shadows and the highlights.

Depending on how you have LR set to display a RAW file when an image is first opened the 8-bits of information your monitor can display are usually taken from the middle of the full dynamic range. Moving the exposure slider to the left doesn't synthesize new information that wasn't already present in the RAW file, it just shifts which range of values in the RAW data are depicted between black and white. The value at which full saturation is displayed is increased, but so is the value that is rendered as full shadow (black). Moving the exposure slider in the other direction lowers the black point and white point so that details of shadows are made lighter at the same time dimmer highlights are displayed as full saturation (white). Sliding the highlights, shadows, or black sliders increase or decrease the exposure for only the pixels that fit that part of the luminance range in the image.

You can do the same thing with contrast, color temperature, saturation, etc. There is no way for an 8-bit monitor to simultaneously display all of the information contained in a 12- bit or 14-bit file. When you move the sliders you aren't telling the program to synthesize something that isn't already in the RAW file, you are telling the program what parts of the information in the RAW file you wish it to display.