I don't know much about contract negotiation, but for organizing "high touch" doesn't begin to describe it! The labor organizer's job is to convince the worker, who likely and often rightly fears for her job if she actively and publicly supports the union, that it's still the right thing to do. Not only convince intellectually, but psychologically prepare the worker to stick with the union effort in the face of a concerted effort from the employer to defeat it. To do that the organizer needs to ask the right questions, listen carefully, build trust, and finally push, and potentially do this repeatedly with the same person. It is psychologically demanding and not everyone can do it; I tried and I couldn't. A chatbot cannot convince a factory worker with kids to feed that he needs to stick up for his coworkers who in turn will stick up for him. All that said I think there is room in the process for profitable automation, but it's auxiliary to the main work.

If you're interested Jane McAlevey's book Raising Expectations and Raising Hell is a good introduction to union organizing.