Every messenger apps (fb messenger, slack, telegram, skype) has its own chatbot directory list. Also, for example in fb messenger, you can run fb ads campaign to promote your bots, but the convertion rates are not very well.

In my case, I use the bots who helps me in two ways: - News. I use it like a service to receive the latest news once per day. - Productivity. I use some slack bots that it helps me for productivity and also my team.

Like the apps, if the bot is useful for the users, they will use it.