planenut - could you clarify slightly what you're asking ?
Do you mean why do the likes of Easy / Ryanair not become a carrier offering long-haul flights around the world ? AirBerlin already offer (or used to offer!) some long haul flights from Germany. The economics allowing a LCC to offer short haul fares much cheaper than traditional airlines change significantly when one looks at long-haul flights.
Or are you asking why Easy / Ryanair do not set up LCC airlines in other areas of the world besides Europe ? In many parts of the world, there are restrictions that to offer domestic flights no more than (e.g. 25% in the USA ) of shares must be owned can be owned by foreign nationals. Further bilateral treaties between countries often govern who can fly where and how often.
Ever since the EU made air transport within the EU a single market (i.e. no restrictions that shares must be owned by nationals of a particular country in order to operate flights), this has inevitably led to consolidation - see the case of AirFrance / KLM or Lufthansa / Austrian. The LCC segment of the airline market is no different.