There is a great reason if you bake. Baking is chemistry; you need a modicum of precision. Recipes using eggs measure the liquid volume based on the average produced in "large" eggs. While medium eggs are less liquid volume, using them will not keep your bake from rising or baking-through adequately. Jumbo sized eggs add enough more moisture to throw off your bake. You cannot just adjust your other liquid volumes and hope for the best because jumbo eggs add enough extra egg to alter the texture of the baked good.

Example: Your recipe calls for 4 eggs. You use 4 jumbo eggs and you'll end up with the added volume of around another egg, meaning you've added the volume of about 5 large eggs. Then, you're shocked when your cake texture is stodgy.

Plus… think of the poor hens, dude!