There is a new Behavioral Event functionality for Marketing Enterprise, and the old one is marked as a "legacy". The new one supports only Delay until event happens feature on workflows. Knowledgebase article explains how it works, but currently, you can't use events for anything else but delays.
We want to use Behavioral Events also as a trigger – not delay. For example, when event X happens, we want a Slack notification.
This is an important feature for especially Sales and Service, when something critical happens. Also, Marketing people can benefit from this. When notification reaches proper persons, they can serve better customers in real-time.