I'm purely guessing here, but I would suggest that the aversion to using a progressive platform like an iPad would risk Apple moving it forward faster than the companies designing apps can keep up.
Using an iPad in the cab? Took it home & let it update itself to iOS version whatever? Drilling app won't work for a week until the techs can rewrite the software to match the update? New model out? Doh!
Of course there are issues and hurdles to overcome, but ISOBUS is hopeless at the moment and they have been trying to make it compatible with itself for 20 years. A fresh start is required.