For some people anyway. They figure they can cash in on something that hasn't been done before, which isn't always a bad thing. I just think one shouldn't have an idea and have it become a reality only for it to make money. It seems that if an idea is just being used to make money, then that takes the enjoyment out of it. Ideas should be used to produce something fun for someone, with no anticipation of making money off of it. That was the case with Kevin Eastman and Peter Laird when they created the Ninja Turtles -- they didn't think they were going to make money off their idea since they were basically doing a parody of Frank Miller's work on Ronin and Daredevil. Am I saying that one will make money off an idea if he or she doesn't anticipate to do so? To some degree. Anticipation did not determine Eastman and Laird's success -- originality did. No one had thought of crime fighting mutant turtles before, which was made their idea stand out in comparison to, say, a rehash of a Spider-Man story.
Another thing that comes to mind is when ideas are stolen to make money. I'm not sure how often such a thing happens or even how people can get away with it, but it seems rather dishonest. I just hope that in order to avoid stealing an idea -- that is, one gives credit to the person who has their idea represented in, say, a video game -- one acknowledges what his or her (similar) idea comes from. Not acknowledging the fact that one borrowed some ideas from a previous work is like saying, "Oh, no one'll ever notice." People do tend to notice, though, and they can end up feel like they've been cheated into buying something which has similar concepts to something they already own. I've noticed similarities between Legacy of Kain: Soul Reaver 2 and Prince of Persia: The Sands of Time. I've had The Sands of Time sitting in my game drawer for a much longer period than Soul Reaver 2, but it wasn't until that I started playing it again that I noticed its similarities to Soul Reaver 2. While I don't mind the similarites between the two games -- the Soul Reaver and the Dagger of Time, for example -- I think that a game can lose its appeal if relies too much on the similarities it has with another game. Furthermore, I hope Ubisoft, the developers of The Sands of Time didn't simply rehash the Prince of Persia games so they could make money by stealing ideas from Crystal Dynamics, the developers of Soul Reaver 2. I'd imagine it's the other way around where Ubisoft borrowed some of Crystal Dynamics' concepts with permission to avoid any unecessary lawsuits.