just engineering decisions based on tensile and shear, so they can't standard size down, and don't want to standard size up. bike in the shop, you have all the tools for anything encountered, but traveling, you don't have that selection available. once the decision is made to produce a largely bolt-together front end instead of welded, then you might as well standardize fasteners, weld nuts being a bonus. as i've said, you're not likely to make a field fix on an all welded front, it's even tough to get one straightened out in a shop setting. with the bolt-together, i can pull it apart, beat the individual pieces straight on just about any flat surface, then bolt it back together and advance.
now i'm getting visions of pounding a pile of junk in shape on top of an abandoned railroad track out in BFE. either that or a flat rock, lordy, knock on wood.