There's nothing stopping you from doing your development, testing, and deployment against the base OS on your Pis.
Even beyond pure learning opportunities, though, there are good reasons to containerize applications even on a system as low-powered as a Raspberry Pi.
For example: if you have a k8s, Docker Swarm, Nomad (disclaimer: I work on the Nomad team @ HashiCorp), etc. orchestrator in place you can keep workloads up and running even as you take down individual machines. (This can help a lot for OS upgrades, replacing failing hardware, disk upgrades, etc. on a running cluster.)
Likewise, you can develop + test your containers on a more performant or convenient machine (like a PineBook Pro, or VMC on a Chromebook) and deploy to the Pi(s) without having to manually map your FS layout, dependencies, etc. to Raspbian or another Pi-specific distro.
It's not something you _need_ to do, necessarily, but neither does that mean there isn't value, esp. for folks already comfortable with a container-based deployment workflow.