interstellar travel is so pasky, irritating and slow. A civilized culture might well cultivate such systems so that they could have a huge number of worlds in easy range of each other.

Allow them those abilities and you might as well be importing already inhabited worlds from wherever you like, which saves time.

Yea, but science fiction seems cooler when a story uses some plausible setting. In any case, another alternative is just to have a large planet with habitable moons in its orbit. Perhaps the planet itself is dead and too hostile for life, and the residents of the moons travel around it to get to civilizations on other moons.