There already are a lot of activities that are in place to motivate players to roam about. For example, maps, catching bugs, digging for supplies (bombs/arrows), pyrat quest, searching for new hats, i can go on.

Also, there are plenty of free items. You just need to work a bit for them. The Big Blob baddy gives free items. All you need to do is take it down and you get free items or gralats.

Forgot to mention, players can loot and then sell it to the cpu/npc's(whatever those characters are) all over graal.