[viraptor]

I'm happy using docker. What I think you're missing is dependency changes and general ease of running CI. (this may not apply to projects which have long-term-stable base and just add lots of code)

1. When some native dependency change is needed, you have to make at least 3 changes: the actual code update, the packer script, and your Jenkins worker. Unless you empower all devs to change this, you have a bottleneck. And it only really works as long as you can have both versions of deps installed concurrently.

2. It's hard to really run tests in production like environment. Spawning new instances is a long and annoying step. Spawning a docker container is trivial in comparison.

3. It enables devs to run meaningful tests without having the exact same OS on the desktop like what's running on the servers.

Docker has other issues, but for these use cases it really solves problems.