why if the offense fumbles into the end zone and it goes out of play, it's the defenses ball? Anywhere else on the field, if the offense fumbles and no one recovers before it goes out of bounds, it stays with the offense. Why is it different if you fumble into the end zone?

Maybe it's because no one knows where to place the ball if that happens. But it just seems odd that in that one situation, if the ball goes out of bounds, it goes to the other team.