Take the USB port as an example. It's ubiquitous; practically everything either has one or plugs into one.
Similarly, if you want to build a multi-vendor market for almost anything, one of the best things you can do is to find the natural divisions of responsibility and insert standard interfaces into the boundaries between them.
One example, in the context of cultibotics, would be the connections between robotic arms and tool units that attach to them. What physical form should the connections take? How much force should the mechanical connection be able to withstand or apply? What services should the unit be able to expect from the arm? What signals should each understand or send to the other, or pass through to the CPU? Would the arm supply water, or should any unit making use of it have a hose connected to it in addition to its connection to the arm?
Detailed answers to these questions would fill a thick book, which is what it typically takes to specify a standard. Moreover, chances that any standard organization which undertook to fill in the details would decide that there would need to be several such standards, to accommodate scales ranging from very small to very large.
But given a set of well-defined standards, you'd be able to buy a robotic arm from company A and a tool unit complying to the same standard from company B, and have good reason for confidence that you could just plug them together and have it work seamlessly.
Until now there hasn't been much need for standardization in agriculture. The prime examples of what there has been would be power takeoff, hitches, and hydraulic connectors, all of which have been standardized by the ISO, which makes it the most likely candidate for tackling standards for robotics in agriculture.
Of course the ISO isn't going to get involved until there's at least the beginnings of a market and more activity than sparse experimentation, so it behooves those who do get involved early to cooperate with each other to develop ad hoc standards which are in the public domain, royalty-free, or available for low-cost-per-unit licensing, suitable to the bootstrap nature of the field. These ad hoc standards can later serve as the starting point for formal standards.