IRC used to have all kinds of these bots back in the day. Mostly for downloading software. I remember even building one for the hell of it when I got bored one summer.
What worries me is that that this mirroring also applies to the erection of giant walled gardens as well. It seems curious that this current bot-bandwagon has exploded after the XMPP interoperation world imploded. Different APIs now to build bots for Slack, Facebook, Google, Skype, etc...
I think it's in-combo with the whole AI/automated personalization as well. It used to be very difficult to do intelligent bots, but now you have tensorflow/caffe/word2vec frameworks that come built-in with NLP
With apps, you downloaded things to do things. With bots, you integrate them into things, so they'll do it for you. (Save extra step laziness)