if "we" designed tractors they would be 15,000 lbs for a 25hp tractor, they'd never (ever) break, they'd be easy to work on, as big as a house, and about as expensive as one. And if JD built a 25hp tractor, it'd be smaller cheaper easier to use better looking, but unfortunately harder to work on. BUT which one is going to sell more?
There is a lot to making things and it's a constant battle between the enginerds and the marketing team and the technicians in ALL types of equipment (cars trucks tractors atv's side by sides lawn mowers everything)
Golf cars are similar. How many different types of 8v battery are needed? 3 that I know of and 2 are so similar that an untrained eye can't tell em apart but there IS a difference.
A dodge intrepid battery needs to be different than a Ram battery...they are located differently in the vehicle, held down differently and they are hooked up differently, the intrepid v6 engine takes up the entire engine bay and there ain't much place for a battery so where they decided to put it is hard to get at, and requires different sets of constraints than a ram does.
a 551MF battery and a 551RMF are identical EXCEPT the R has the posts swapped, earth on the left and plus on the right. A ZD21 needs the RMF but a BX can use the MF as I recall, because of how the tractor is designed. Just a few thoughts for what it's worth