User blog comment:Kraykan/One piece technology/@comment-4754162-20120720011728

That is what makes each arc (islands / locations) unique and fun to read (as a manga). Not to say that the technologies could not travel across the OP universe (e.g. the recording thingy Soul King use to record his music to fans is kinda the same used by Skypiea), in fact nothing could have stopped it from travelling actually but if its readily available everywhere then where is the fun in discovering the queer (Neo-chan, it means "different and weird" here ok) stuffs as we read on, yeah?

You have also mentioned a good point, travelling across the grand line (paradise & new world) is no easy feat, so the chances of things spreading are lesser likely as compared to our (reality) world.

Certain things are kinda too advance and cutting edge (vegapunk's stuffs) and that could very well be tightly protected (not sure why the abandoned lab Franky went into was not guarded at all though).

Lastly, try not to overdo the thinking about logical stuffs in OP. You will find out that you sometimes need to just accept it for it. ^_^