I don't think it was that they were economically tied to those planets, as many people would be today. Like you said, in a world with FTL drives, transporters and replicators, relocation would be fairly simply.
It was that they were emotionally tied to those homes. They built something out of nothing, raised families there and didn't want to just leave it all behind to start up again somewhere else.
But besides that, it's their property and the Federation just swooped in and ordered them to hand it over. Many people would have a problem if their own government did that to them.