Because crafting is fun. Especially Game-related crafting. And 3E monster manual looked cooler.
Now that I've been moving towards using maps and tiles as terrain instead of 3D terrain, as most of my games take place somewhere else than at my home, I've had an itch to craft something. Seeing some very cool Dice pouches and pondering what would be optimal way to categorize and store my minis gave me an idea of making a Monster Manual -style miniatures box for my core miniatures collection.