Unless something has changed recently, my understanding is that you do not need to provide a working prototype under US patent laws. You just need an explanation on paper of some kind that would allow a third party to be able to build whatever is being patented.

Of course, someone has to look at the explanation to determine whether the prototype could be built and be functional to have the patent granted. But who has time to deal with all that noise when you just grant the patent to let someone else deal with it?