For trivia WP will generate all registered sizes for every image natively. While this doesn’t quite seem optimal, the recommendation (if one might call it that) to deal with it is “get bigger disks”. 🙂 If size isn’t a concern you can just go with it.
The typical solution takes a little different angle. Instead of generating specific sizes on upload, the sizes are generated when they are first requested. So the specific combinations of image and size which are never requested are never created.
There are several implementation like that around, but I hadn’t used any recently to recommend specific one. You might get better luck searching for keyword of “thumbnails” rather than “sizes”.