The problem is that people love government force and meddling when it gets them something they want, but are against it when it's something they don't want. They don't see that any money or power they give the government today to, say, enact mandatory recycling laws or mandate health coverage gets used the very next day to create restrictive building codes, eavesdrop on all their telephone or Internet use, or fly halfway around the world to drop bombs on children. Government power is fungible, and needs to be kept as small as possible – even if it means giving up things that you want the government to do for you.
What people don't know is that government power is not vested in the politicians. They come and go every couple years and don't have much of a chance to set up significant power structures. Political power is in the bureaucrats, and it is here that we find the true reason why *all* government power gets used for bad ends.
Bureaucratic "skill", such as it is, is simply the ability to read and zealously apply whatever rules you are charged to enforce, and as such a "skilled" bureaucrat can work at the EPA one week and the DHS, FDA, EPA or BATFE with a week of training. Say you create a new government department and staff it entirely with a broad spectrum of people, from the nice people that don't seek power to budding petty tyrants. Because being nice - taking special cases and making exceptions - takes longer than simply blindly enforcing rules and smashing flat those citizens that oppose you, the petty tyrants will be more efficient and take over the organization eventually. Therefore, all government departments must eventually be staffed entirely by petty tyrants, even innocuous ones like the Patent Office and the Department of Education.
Now, how does the power you give a "nice" department like, say, the Department of Education get turned into the power of a "nasty" organization like, say, the BATFE or FBI?
One has to realize that the strength of an organization is in the number of bureaucrats that it commands. Each bureaucrat is only capable of enforcing a fixed number of rules actions in their 5-hour workday, and it is the number of enforcement actions that determines their advancement, so they are incentivized to hand down as many enforcement actions as possible. Again, this is a skill. The greater the job market for bureaucrats, the better the competition for people with the bureaucrat's skill of zealously enforcing rules. Therefore, the bureacrats within the system are incentivized to perform better and better the more bureaucrats are added to the system, *no matter where you add those bureaucrats*, as again they can work in the Department of Education just as easily as they can in the IRS or the FBI. Of course, it is the frontline people that actually have useful skills in the area of science, law, medicine, or whatever, but it is the middle managers that determine where they go and what they do, and a middle manager is a middle manager no matter what department they work for.
Therefore, it's not possible to give certain "good" areas of government more power without making the other "bad" parts more powerful as well.