Technically there are standards, but you know how that goes in the real world... Funnily enough, a friend bought a new tractor and planter, both from John Deere, and they weren't even compatible with each other. The tractor needed to have the cab removed to install the necessary hardware (ethernet) to be compatible with the planter.
> have been standardized forever
Hydraulic hose couplers didn't find common adoption until the mid-80s/early-90s, which is surprisingly late.