"Not much else", like no customers for the electricity produced? /s. Yes, there are regions for example in the US, where putting up solar cells would be very cheap. But then you have to run power lines to where your customers are. That can be 1000 kilometers or more. Doable, but that certainly affects the economy of things. And yes, I think the US should put large solar farms into its deserts. And of course, there are countries, where land is not cheap and there might not even be deserts. Here in Germany for example, basically all land is somehow used.