As Dave and OldhikerQ both pointed out, it serves a personal interest. Whether it is to pass winter time being involved in analysis of next years fun or satisfying the technical aspects of our being, it is fun for those who play at this detail. Playing with spreadsheets is fun, even for me when I do it for a living, but I find more enjoyment from a business perspective. I love programming with VBA because it's fun to create, especially when it saves me much time and effort creating the data reports I need to produce and tracking historical data in perpetuity. It's not everybody's cup of tea, in fact, as Dave rightly points out, it's a tool that very few really know how to use and a technical level very few people enjoy.
In my early 20's, I used to graph elevation changes for hikes by hand. There was no Excel and Lotus 123 was in it's infancy along with the personal computer to run it. I did nothing with the information, but I had fun measuring distance and calculating elevation and it engaged me in the process. By the time the trip came up, I knew the map like the back of my hand. Obviously, there are many ways to become that familiar with the trip. This method does it for some.
I can easily see the value for a photographer. I haven't studied his data very seriously, but if it's not there, I'd find value in adding data from the Photographers ephemeris to indicate time and direction of sunrise/sunset,etc. Then research features I may want to photograph where I'm at during the best lighting situations.
Nothing good ever came from should.