Hubot was EPIC
Hubot swept the ChatOps sphere by making it super simple to write your own bot.
It had tons of plugins that could integrate to almost anything.
Just shoot up a node instance on one of your servers, and BOOM, you’re hubot-ized.
Suddenly you had a presense in your iRC / Chat that could not only notify you on events, but also take action.
Ack that Nagios alert, Chart that usage with Graphite, you name it.
Then came Slack and HipChat
HipChat, but mainly Slack, made it even easier by having integrations available on the platform level.
You no longer needed any process running, Slack would take care of everything for you.
Not only that, Integrating new Services with Slack is usually no more than 3-4 clicks away.
A simple no brainer that JUST WORKS™.
If you needed anything more, Slack created a super simple bot API you can run, that doesn’t require the entire Hubot framework around it.
Is it only Slack?
Nope, more and more services strive to have simple integrations to you chat.
Slack just does it better, and is so popular that most services WANT to integrate Slack as quick and simple as possible.
So Is Hubot Dead?
Hell no, whenever you need something quick that does more than notify, Hubot is still your best choice.
When Slack will host your custom coded bots, Hubot will indeed be in trouble.