But that's not true at all. The genesis for DI was nothing close to that (as I learned it). DI's main purpose isn't testing, it's flexibility. DI isn't there solely for testing, or if it is, you're probably missing the point of it.
These are "enterprise" Java apps with Spring, etc.
I've had better luck and cleaner code without it than with it.
A good DI container can make it much easier to follow a pretty good amount of general best practices. Single Responsibility, DRY, and Open-Closed Principle to name a few.