Here are the few places I’ve used it in:

Create isolated AUT instances
– We have separate DBs for different AUT versions
– Using docker can instantly create multiple AUT instances
– Different approaches to do it, one can be to just hook up multiple DB versions to the same app server

Multiple execution environments

– Selenium grid(s)?
– If your automation tool allows, can create multiple execution environments
– Can hook them up with Jenkins and everything will be done on the fly

I’m sure there are other uses where the AUT is NOT containerized and we can still leverage docker.

Have you tried something different? would love to hear..