The main "meta-reason" is that if the Governments would use more Handwavium, there would not be any Fenspace. Because Earth has much more resources to exploit, so the whole scenario would fall apart.
One possible "in universe" reason for this is that Handwavium does not react well to bureaucratic organizations. Which means that the organized exploitation of Handwavium often hits "creative" roadblocks. Another reason might be that Governments do not want Handwavium to spread through the Industry, because they fear a complete lack of control.
One possible "in universe" reason for this is that Handwavium does not react well to bureaucratic organizations. Which means that the organized exploitation of Handwavium often hits "creative" roadblocks. Another reason might be that Governments do not want Handwavium to spread through the Industry, because they fear a complete lack of control.