Most private jobs are like that. Most federal government jobs are not (the part about being fired at will). For a reason, to prevent Political Patronage or the Spoils System, where jobs are given to political lackeys, as opposed to going to the most qualified applicant. en.wikipedia.org

We passed laws to stop patronage because of the negative impact it has on our government, where employees who are good at their job are fired only to be replaced by a different idiot every four years when someone from their party wins office.

The purpose of [Schedule F] is to increase the president's control over the federal career civil service by removing their civil service protections and making them easy to dismiss, which proponents stated would increase flexibility and accountability to elected officials. It was widely criticized as providing means to retaliate against federal officials for political reasons, impede the effective functioning of government, and providing risk to democracy. It has been estimated that tens or hundreds of thousands of career employees could be reclassified, increasing the number of political appointments by a factor of ten.
en.wikipedia.org