Email Programs can be nested into Event Programs and Default Programs (this thread has some points as to why this can be beneficial Nesting Email Programs in Default Programs), and Default Programs can be nested into Engagement Programs (here's a good doc on some reasons why this can be useful: Adding a Program to an Engagement Program Stream - Marketo Docs - Product Documentation).
As your use case is an event, the first link will be most key. The main question for you will be whether any of the benefits they outline are important in your specific use case (e.g. access to A/B testing functionality). If yes, consider giving it a go.
+ if you'd like to see them in action, some of the program templates that can be imported from Marketo's program template library include nested programs (I believe the complex nurture v2/3?)