Also, for small companies, it may be the only option as they cannot be available 24/7.
In my experience, most tech-savvy people do not want to call or chat. They only resort to those options when they can't find a way to do what they need to on a company's website. There is another group that wants to talk to a real person regardless, but they usually prefer to call. I'm not aware of any group that wants, or has their needs best met, by talking to a chat-bot.
Have plenty of experience helping companies set up chat bots properly, and watching customers actually talk to bots and have their questions answered by bots. There are always some people that would automatically escalate to human support every time and not bother with the bot, but there's also a fairly large percentage of people who would go through with the bot.
Can we also dispense with the second-hand reassurances that "someone" would disagree, and replace it with first-hand testimony from someone who actually prefers the chat bot to chatting with a person?
Effective chatbots tend to triage requests and point users to further information, rather than fully solving the issue on their own.