I see not being able to go anywhere with a cart as a benefit. This will lead to 'continents' having roads leading to ports, where carts drop off goods for boats to pick up. Boats pick them up and take them to a different port, where they can be picked up by other carts and carried to wherever the goods are headed. Think Transport Tycoon Deluxe.
Also sabinati is right. If you don't have the skills to cross a river, chances are whatever is on the other side would kill you anyway.
Edit: Also newbs don't need to find and build new mines, they need to find and join a town.
Sweet Benjamin, since thou art young,
And hast not yet the use of tongue,
Make it thy slave, while thou art free;
Imprison it, lest it do thee.