I had a boss who used to bring French toast casserole to every company potluck. It was delicious (and a flavor that I thought of when I made my own French toast casserole recipe). Instead of cubing the bread, she would cut it into slices, then put those slices in a casserole pan and pour her egg mixture on top. It's good that way. But when you serve it, you're serving slices of French toast and need a knife and fork to eat it. With cubed bread, you can scoop it and eat it with a spoon. So that's less utensils to wash after. And, it just makes this feel like a more fun, special occasions type of meal.