the hub is softer than the axle
the axle is pretty soft, it has to be in order to "spring" a little, to dampen torsional loading. Otherwise it would just break off.
they could make the hub harder than the axle and then there's a chance that the next gripe is that the hub is too hard and takes out the splines on the axle, hey let's sue kubota for making an inferior product it's a factor defect, take it back and demand a new machine, etc etc.
think about how the hub is made and what it does. It's gotta hold up to dirt/grime/mud/poo/pee/typical farm use among other things, and it's gotta endure that--in combination with the WEIGHT of the machine (1100's are what? 2500 lbs?). And it's got a manufacturing aspect too, in that it has to be made strong enough to get through a reasonable length of time without failure in reasonable operating conditions yet still be inexpensive enough not to pose a significant price increase in the overall machine's cost when new, so that the manufacturer and dealer can turn a profit without excessive warranty costs.
similar to whitetiger I serivced TONS of RTV's over the years, hundred or so a year on average. Out of those I put maybe one or two hubs on per year and those were generally 'obvious' as to how they were taken care of (nonexistent maintenance). Most of the time the hub jobs had MUD packed in to the wheel dish so thickly that you couldn't see the lug bolts, and on the back side there was a hole in the mud/poo that the axle ran through and that was it. Ya know if people would take better care of their stuff us techs would have less to do, and these forums would be a whole lot less active.
I actually quit kubota dealer work because of stupid stuff like that. As a kubota tech, you are always: too expensive, too slow, too ugly, too stinky, whatever. It was very very rare to have a customer show up with a smiling face and I certainly didn't forget those. In one day, it wasn't uncommon to have to answer 40-50 phone calls about people mad because they read online that there was some factory defect (hub, or whatever), and about 25 or so in person visits, very rare for any of them to not be in a pissy mood. It wears on you. It is depressing.
Shop I work in now does not see one single customer in the shop, nobody smokes (thank goodness), it is heated and air conditioned, it is clean, quiet, and best of all NO KUBOTA'S