The overwhelming majority (like 98% or more) of support requests are from people who have not read the documentation and are asking about something that is well-covered within it.

Chat bots can't (currently) eliminate the agents who exercise critical thought and report bugs, but for any company large enough to outsource "tier one" support to a call center overseas, the chat bot would actually be a big improvement.

More likely, a lateral move rather than a big improvement. But you're right -- companies that outsource the support to crappy call centers are companies that barely have customer support at all.

There is a distribution of users. Definitely some users are better off (no matter how good the chatbot is) using the FAQ or websites. Some people are not chat interface orientated.

Some people would benefit from a very powerful and effective chatbot. The grandmother you cite for example! But the problem is that almost all chatbots are incompetent and really function to:

1) deflect users

2) bolster the innovation credentials of the organization or sponsors for the project.