Schwalbe Marathon is Schwalbe's top of the line touring/commuting tire.
Its virtually indestructible. Of course with that comes a significant weight penalty but if you're in the middle of nowhere, the last thing in the world you want to do is fix a flat.
That's why the Marathon is the favorite tire of tourers and commuters who need something reliable.
This is not to say the rest of Schwalbe's line is inferior.
If you don't need the protection of the Marathon, you can get by with lighter tire.