Why? They might be much better at inventing things than starting and running a business. The stated goal behind patents is to advance the sciences not to create businesses.
My understanding is that the goal is to advance society (not really the sciences) by enabling someone to produce their invention so society can benefit from it. The patent protects someone from having that invention copied as soon as it is put to use, which provides motivation to spend the time inventing it.
To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;
