Sure, but the dev already has experience with the tech behind a chat bot, and may not have the experience needed to make a web app as easily. Think about all t

Sure, but the dev already has experience with the tech behind a chat bot, and may not have the experience needed to make a web app as easily. Think about all the "obvious" steps involved (text input, message chain display, page/server communications), the extra features FB messenger has (in-message buttons); then the issues with cleanly displaying on multiple screen sizes; and then you start getting into the fiddly bits like page reloading, form submission failures (say, due to internet disconnect).... ...All of that is done for you. You just need to have the meat of the program (the chat) and you're good to go. Makes a lot of sense, actually.