Docker for example is used on the Kbin project. They’ve created a docker image that gets PHP, Posgres and all the other services needed to get up and running with the project.
Without that image you’d have to manually get everything up and running and while I’m sure some people are comfortable jumping into a new project, having a single image that does most of the legwork means you can attract developers who just want to get started right now.
This is super handy for UI/UX/Designers/concept focused people who need to get the project running locally quickly.
Good, glad this shithouse comment is getting the proper downvotes