And if you are wondering why Nxt is having so many implementations, you are still have a silo mind where each crypto is an island with the devs as head chiefs who decree who can do what in their domain.
Nxt is an open platform where anyone can build what they want on top of Nxt, and they are. See Sergey's project above
So to continue the analogy, Nxt is a new continent where anyone can come in and set up their own city state based on the topology (Nxt core) as they find it without permission.
Maybe they will settle on the coast to make it easy to do a lot of trade with others (i.e. use Nxt Asset Exchange).
Maybe they will settle in the mountains and help others with otherwise navigate difficult passages (i.e. use Nxt Smart Contracts)
Maybe they will settle in a metropolis to sell their goods (i.e. use Nxt Marketplace/Free Market (decentralised ebay)
One by one new, external devs are coming on board and colonising this new world