We use them because then what’s running in prodcution is 100% the same as is running locally when testing the application.
You can hardly get there using Ansible.
With Linux competency and some thought put into design, you can find a balance between reproducibility and ease of use with Ansible. Easier for me and those who agree with me to configure and debug a Linux host vs. debugging and configuring Docker to be as flexible as running it straight on the OS.
It’s not an impossible task to harmonize configurations with Ansible. It definitely takes more thought than Docker and that’s where the competencies of the team count.
Only if you’re running the same kernel.