As with many 'organic' channels, the relative reach of your audience tends to decline over time due to a variety of factors. In email's case, it can be the over-exposure to marketing emails and moves from email providers to filter out promotional content; with other channels it can be the platform itself. Back in 2014 I wrote about how "Facebook's Likes Don't Matter Anymore" in relation to the declining organic reach of Facebook pages. Last year alone the organic reach of publishers on Facebook fell by a further 52%.
The term "ChatterBot" was originally coined by Michael Mauldin (creator of the first Verbot, Julia) in 1994 to describe these conversational programs. Today, most chatbots are accessed via virtual assistants such as Google Assistant and Amazon Alexa, via messaging apps such as Facebook Messenger or WeChat, or via individual organizations' apps and websites. Chatbots can be classified into usage categories such as conversational commerce (e-commerce via chat), analytics, communication, customer support, design, developer tools, education, entertainment, finance, food, games, health, HR, marketing, news, personal, productivity, shopping, social, sports, travel and utilities.