Long distance communications in the Republic/Empire often seem "fuzzy." Possible in the past it was worse, requiring representatives to have autonomous decision making authority. As communications somewhat improved they simply maintained the practice. Being a Jedi required possessing a natural ability, they couldn't be recruited from the general population. Rising to the Jedi council could have been (at lest partially) dependant on how powerful you were with the force, a determination a "outsider" couldn't make. In terms of percentages, they spent less of their known history in civil war than America, Britain and quite a few other nations.