It's happening. Here are some automated weeding systems in use in central California.[1] "All these machines use a camera to detect the crop, a computer to make decisions on which plants to keep/remove, and then activate a kill mechanism." Most of these things are implements towed behind a tractor, not robots. These implements seem to be built up from a row of detector/computer/actuator modules, so if a module fails in the field, you should be able to unbolt it and bolt in a spare, then take the broken one in for repair. Electronics for a module is probably cell phone level.

So far, they're not as flexible about weed/plant detection as they could be. But there will probably be a training system where you go out with a cell phone pointed down at the field, swiping left for weeds and right for plants, until the machine learning system is trained.

There's a lot that can be done, and is being done, by hooking up inexpensive vision systems to actuators on agricultural implements. Here's a nice example - a cultivator which is stirring the soil around each plant while not touching the plants.[2]

The main problem with automated vegetable harvesting is not that it can't be done, but that for some crops the infrequently used machinery isn't cost effective compared to hiring large numbers of people for short periods.

[1] https://www.growingproduce.com/vegetables/automated-weeders-... [2] https://www.youtube.com/watch?v=DhqNmRuBPsw