It's not immune, but governments tend to be formed with the mandate to prevent those exploitations. This makes them more resistant to those desires. The more people in that government, the more social pressure there is to keep those exploitations minimal so that they can remain undetected.
That's what the difference between a government and a business is. They are otherwise the same.
I don't see how staying in the office for 4 years practically indefinitely, makes you more resistant to exploit the opportunities it provides. On the other hand, when business does something customers don't like, it loses customers, money and goes out of business very quickly (unless it is bailed out by the government!).
Also, in my view, the problem with your argument is that your expectations of government (preventing exploitations) is rather different from reality (picking winners). Just because many people believe that government is supposed to do good, doesn't make it act this way.
A government has a much harder time being exploitative than a business does. To the extent that a government's personnel are involved in businesses, the government is corrupted and its resistance to exploitative desires will break down.