Another advantage of real printed books is that real printed books are also inexpensive enough to be routinely given as gifts to small children, even in dirt poor families. IMHO, this is important as early readers are often young enough to be ridiculously rough on pretty much anything they play with, electronic or paper. They also lose things a lot. The difference with paper books is not that they're more durable, but that one book getting damaged or lost doesn't destroy a child's entire library and doesn't have a high replacement cost.