Perhaps due to the fact that the concept of screws in Japan was never independently invented but discovered in an imported weapon almost into the modern era, or due to developments in mechanical engineering that defined postwar Japanese cultures, but anyway Japanese population is kind of obsessed with screws for some reason.

Japanese thought process of a machinery is it is made of machined metal and infinite numbers of 3mm screws. Look at a Casio watch. There should be four Phillips screws on the backplate. Two extra on sides and four more, if it's rubber exterior ones. A Rolex, has zero. Just like that. First choice of fasteners to join any two arbitrary parts is a pair of 3mm screws. If a joint has to articulate, there should be a pin on one side, hole on the other, and a 3mm screw to seal off the end. If it has to slide, tapped hole on a bar and a half threaded screw.

It's cultural thing. I'm from Japan so an "eerie" lack of screws still confuse me sometime when disassembling non-Japanese things.