When making this statement, it would be helpful to add the "in comparison to" part. People who can't see the benefit of containers may actually live in a world where they have standardised repeatable build environments without containers (it is possible after all).

For me containers are convenient for the task of specifying the repeatable build environments. It is also useful for caching those build environments and distributing the cached artefacts in a versioned way.

To be honest, if you are working with only 1 or 2 build environments, I don't actually find it particularly more convenient that setting up something without containers. Often I find it even wasteful because you usually select fairly large base images (hundreds of megs) even when you only need a few things. You can build a really streamlined image, but it's a fair amount of work.

However, if I have to coordinate many "microservices" that are talking together via TCP/IP and implemented in several different versions of several different technologies, it's a life saver. Normally I try to avoid this circumstance for reasons I wish were obvious to others. But of course we know that it is not obvious to others and so I appreciate being able to use containers ;-)