Celebrities and babies have two things in common: they both don't want to be watched as they eat.
Imagine walking up to someone famous at the local all-you-can-eat buffet. What reaction would you get? First, the ol' "Not me, man, wish I was though." Then maybe a "Okay, fine, it's me, but I'm with my family." And then, the cruel glare and the request for the bodyguard to escort you from the building.
We all know the only bigger baby than an celebrity is an actual baby. So avoid the scene, and cover your child with a nursing cover! They'll be happy, you'll feel a bit less exposed, and nobody will run across a restaurant and yell WOW ARE YOU JAMES FRANCO???? while your baby is just trying to have some lunch.
And don't forget how stylish you'll look!