What about children? With an appropriate case, it can become a great toy.

The same could be said about books.

That's probably true, but it's the same pattern with most things people buy. Especially toys and gadgets. Gets used once or twice and then sits on a shelf or in a closet.

I think I'd use it more if the drawings were far more detailed, but still kept that napkin drawing look.

Though tbh, I'd vastly prefer a printer that just did this, not a camera. Then I can take normal photos with my phone, maybe even preview what the drawing might look like, and then print it with the draw printer.