Government jobs in the US are very hard to get fired from. You have to actually commit a crime, have a history of gross negligence, or just make a big enough mistake during a probationary period to get fired. Appointed positions are probably the easiest to get fired from as the executive can just dismiss you although a forced resignation is more likely to happen. These jobs also have a lot of long term security so they are hard to get and are sometimes only open for current government employees. The downside is that they pay less than a corporate job but that's fine for some people who just want indefinite tenures.