You've been to every corner of the universe to know that for certain have you? No, that's not really true. There are many examples of where we are seeing signs of decentralization in our own society. The internet is a good enough example. It has no singular "center." It is a mass of connections from all over the planet. Even if you start shutting down servers, there is no "master server" that runs the whole thing. All you need is a similar network, subspace connections, and some kind of software that spread throughout the initial planetary network and took over the minds of the people on that world. In Q Who the Borg were still shown to be breeding, and immediately after birth connecting their young to mechanisms, very likely affecting their minds with a software component. Assimilation would be no different. An indoctrination of the mind with advanced computer software. Probably/possibly corrupted from it's original intent. The Borg were a lovecraftian concept, and it was what made them an interesting and horrifying threat to begin with. Giving them the Queen turned them into a glorified bee hive, with the addition of all her petty individual traits. Not to mention making the borg painfully easy to over come.