* Size: Goose eggs are quite large and fragile. A fox's mouth is adapted for catching and carrying smaller prey. It would be difficult for a fox to maneuver a goose egg without breaking it.
* Purpose: Foxes are opportunistic predators and scavengers. They primarily eat meat, and a goose egg would be a less desirable food source.
* Instinct: Foxes aren't known to carry eggs. They would more likely be inclined to break the egg open and eat it, or to leave it alone altogether.
While a fox *could* theoretically carry a goose egg, it's not something they would do in a natural setting.