Portability is the key for me, because I tend to switch things around a lot. Containers generally isolate the persistent data from the runtime really well.
Docker is not the only, or even the best way IMO to run containers. If I was providing services for customers, I would definetly build most container images daily in some automated way. Well, I do it already for quite a few.
The mess is only a mess if you don’t really understand what you’re doing, same goes for traditional services.