It's a new technology, brought less then a year ago, and most game development takes far longer then 1 year to develop, many developers/publishers don't like adding things half-way through, it's risky, may add more to the development time, cause launch issues if a launch date has already been determined, etc. Tacking on ray tracing rather then implementing it from the beginning is not necessarily the smartest thing to do. It's a little difficult to say that it's easy or not, as yes, it's easy to implement, and if all hardware supported it and you didn't really have to worry about performance, then there wouldn't be any need to put in rasterized lighting, and only ray traced lighting. If this was the case, it would cut down costs quite a bit. But given that currently this is not the case and if a developer decides to do ray tracing they still have to do rasterization methods, it becomes a cost to implement over not. The hardware needs to become more out there and universal before ray tracing will technically cost less (then rasterization) and be "easy" to implement. And this likely will not happen until consoles natively, and effectively, support ray tracing. One this is done, there will be no point to spending more money on rasterization methods, when it looks worse, and takes more time and money to implement and perfect. It makes sense that until then, there may not be a ton of developers deciding to put ray tracing into their games. Other then hoping their extra time and effort gets them more money then they spent on it BECAUSE people wanted to see it ray traced, what is the point? My point in the end is this: It's an added addition, which means it's an added cost to implement, and that's not to be mistaken with being "difficult" to implement, one of the major points of ANY kind of ray tracing is how much EASIER it is to implement since you no longer have to manually put fake light sources everywhere just to make the scenes not look like there are black holes everywhere. This is by definition EASIER and LESS COSTLY, but will only really matter on those fronts when rasterization methods of lighting are no longer implemented in games, until then, regardless if "easy" or not, it's added cost, which means many developers, and more importantly publishers, won't bother.