Why's that? For some derivatives, cash settlement is the only thing that makes sense. E.g., look at their weather derivatives. It's not like anybody wants to take delivery on a petagram of cold air.
The majority use case for Bitcoin isn't using Bitcoin at all. It's speculating on Bitcoin. Those people definitionally don't care about Bitcoin for its own sake.
I'm pretty sure the exchanges are offering these not because anybody actually has forward needs to buy or sell Bitcoin, as they would with, say, wheat. People just want to speculate. For those people, cash settlement is exactly what they're after.