@Sylvhem (disclaimer: I used to work there)

what other folks said, perhaps restated: lots of services/programs imagine that they're the only thing a machine will be running. it's really nice to be able to provide them something that looks like that (your own filesystem, etc), in a reproducible way (hopefully). you can do that without docker specifically, but the presence of a big repository of existing configurations from which to start makes docker attractive for some people.

it's definitely not a magic fix for all problems, and I prefer other approaches for the future :)