I'm not really sure they have been, otherwise you wouldn't see mention of things like The Bell Curve and articles like this popping up so frequently, particularly on conservative web sites and magazines. It also doesn't help that the actual scientific data is stretched, thanks to people like Gould, into a general attack on the very idea of general intelligence. Have you read Jensen's responses to Gould? Further, Scientific American had an issue about intelligence not all that long ago that painted a much less certain picture of current views general intelligence than Gould's proponents often claim exists. And if you want to know why I think letting social implications drive science can be problematic, I'll point you to this old favorite, which comes frighteningly close to how a lot of liberals I've had discussions with online seem to view any linkage between biology and behavior. They consider the whole subject off limits, holding up Gould as support.
As far as how to use the information to "improve intelligence"; I'm not sure exactly what you are advocating. How would you use the data to improve intelligence?
For example, I've read about some recent studies which suggest that that the density of certain brain tissue, as well as size, is important. If we can understand what contributes to intelligence and then understand the environmental factors that might encourage or discourage that sort of brain development, we might be able to give children, either before birth or even after, a better environment in which to achieve intelligence rather than simply guessing with things like "Listening to Mozart makes kids smarter."