I believe there are exceptions such as refusing inventions claiming perpetual motion, and from what I read, refusing inventions of cold fusion as a result of a letter to the Patent Office from DOE.
It is not clear if the lattter restriction has been eased recently.
It has been said patents are worthless until they have been tested in court.
Not quite true. Patents can have a valuable effect of deterring one's competitors from copying your invention lest they be sued for infringement and damages. Not everyone wants to risk the costs involved in using lawyers, particularly if buying a license to the patent is possible