The way I see it, Vagrant does for VMs what Docker does for containers: provides a way to build, deploy, manage, and teardown VMs consistently and without much manual effort. For example, I used Vagrant when learning to use Kubernetes, because I could quickly spin up a 3 node cluster on my laptop and destroy it if I messed up.

If you can use containers for local dev, great, but not everyone can or wants to migrate to containers. Vagrant still solves a very important use case.