There is a natural travel path from country to country, when a person moves from country to country, it is called sequential country living. There can be a series, a number of things, actions, or events arranged or happening in a specific order or having a specific connection
Generally there is a connection between countries common senses leads traveler to visit the next country. If you are traveling through Central America people travel from Guatemala to Honduras to Costa Rica, this is the natural path. While many people fly from Nepal to Thailand only because the airfare is cheap, and it is the simple way to go to Southeast Asia.
Sequential travel is natural, it is traveling downstream, and not upstream, it is the easy and natural way of traveling the world.