Do you really think toys or food or comparable to Facebook? You go into a store, you see the product your child wants, and 99.9% of the time you know exactly what it does. You cannot walk away from a child eating a happy meal for 5 minutes and come back and see them watching a porn video hidden in the hamburger.
Many skills they develop with digital products will be bound to a very small amount of companies. That certainly can be a problem.
This is of course to set up a pipeline for new Facebook users. Doesn't have to be bad, but it is what it is and there shouldn't be naive illusions about it.
Hell, outside of technical circles, I doubt most adults are able to truly understand the scope of what FB does!