No. What you're missing is that nobody uses the negative as the final product, and when you go from the negative to a print, on-screen electronic image, or some other form of output, you are *always* transforming the original in some way. Most importantly, you are manipulating the tonal scale (and, in the case of color film, the color balance). For example, the tonal scale of Tri-X in a darkroom print depends heavily not just on the characteristic curve of the Tri-X film developed in whatever developer you use, but also on the characteristic curve of the paper you print on. You can make radically different-looking prints from a Tri-X negative simply by choice of paper.
What the SilverFast profiles do is make some assumptions about what the characteristic curve of the negative looks like for a given brand of film, plus some other assumptions about what the tonal scale of the scan should be, and it applies a transformation to the scan data in order to convert one to the other. In effect, it applies its own "characteristic curve".
The problem is (1) their assumptions about what the negative looks like cannot be universally correct, because that depends on exposure habits and choice of development; and (2) their assumptions about what the tonal scale of the scan should be won't necessarily match yours.
For color negatives, as Scott pointed out, the profiles deal with the added complication of achieving reasonable color balance from emulsions that vary in a number of ways.
My interest is primarily in B&W, SilverFast is my standard scan software, but for my purposes the profiles for B&W film are pretty much useless. They never match what I want from a scan. So I scan my B&W negatives as though they were positive transparencies, setting the scan parameters to achieve a distribution of tonal values that's roughly what I want. Then in later processing I invert the scan and apply whatever additional corrections I need, depending on what I want to do with the scan.
EDIT: my post crossed with your response to Scott.