Do you use a manual typewriter to create a letter? I feel the same way you do, but people will use things that make their life easier.
Using a computer keyboard instead of a typewriter is far different than using a chatbot, as the bot is doing the brunt of the thinking. The output is not from the poster, who is usually taking credit for it. If people want to use AI to write their posts for them, that's fine, but its dishonest not to let it be known from the start.
Its kind of the same thing as an artist using AI to generate an image for them and then saying "I made this myself."