Perhaps you should go talk to boating communities and ask them. They probably had to move off of shore due to space issues (high price per sqft for oceanfront property)? Maybe it’s cheaper to not live on land? Maybe they like living on the water?
Why are they not 200nm out? Perhaps because there is no seastead there.
Maybe because of the same reason the Floating Island Project is starting Phase 1 in a protected lagoon. To get the engineering down in a protected environment before moving on to Phase 2 where they are 12nm out with more sovereignty but need to deal with the ocean’s turbulence and get all of the engineering kinks out before moving to Phase 3 where it can be 200 nm out in International waters.
At Phase 3, in international waters the island can have full sovereignty. This is the ultimate goal in seasteading. Each platform will be able to detach from the other and create it’s own sovereign community. As more sovereign communities exist, new governance structures can be experimented with as people move to those communities that have the better governance structures and away from those with bad governments.
It is in this way we can improve governance which could eventually in turn be used by current governments as they adopt the best methods.
It will be like how cell phones improve over time due to people being able to choose which cell phone they want. No longer will the assumption be that government cannot change.