They're a computer for things that your laptop sucks at. Draw directly on them, use them for reading, carry them to work sites and use them in situations where a laptop would be super-awkward, put them on sheet music stands, prop them up in the kitchen, hold them up and use their tilt sensors in games, all that kind of stuff.

They're basically never better than a laptop at things laptops are good at (though often serviceable enough that folks don't need both) but excel at other use cases where laptops aren't great.