Any deeper discussion of monarchs would certain break the no-real world politics rule, but I have to counter this one: monarch is way easier to get rid of compare to a dysfunctional democratic government, because there is a clear target.
And I am not sure how freedom and monarch go against each other.
As long as we don't name names (real world nations) we can talk about it.
Monarchs and Freedom don't mix. In our time most of the world's people have freedoms, and Monarch for the most part are just figureheads. Many countries that have a Monarch also have a parliamentary system.
Now go back 300 to a 1000 years back. Monarchs had total control over everyone in their kingdom, no parliamentry system, just the King. The average joe was not even considered a person. Only wealthy people under the king were and even then they had to do what the King wanted.
Monarchs considered themselves appointed by God. It took hundreds of years for people to get ride of their Monarchs or to make them useless figureheads. Main reason why people stared gaining power over their kings was thanks to the Black Death. It killed millions of people and in the end there weren't as meany people. People became less disposable. Technology advanced and less people were needed for farming. So all these uneducated people with nothing to do, ended up learning and learning lead to rebellion. Anyways this is an over simplification.
My point is in a Fallout World a Monarch most likley would be someone that sees themselves appointed by God and would be in total control. That type of system does not sit well with me. I like Democracy, thats why I support the NCR.
True, Kings are a single targer but if that king has armies and has no problem killing their own people then getting ride of them is not so easy.