It’s not. Imagine Immich required library X to be at Y version, but another service on the server requires it to be at Z version. That will be a PitA to maintain, not to mention that getting a service to run at all can be difficult due to a multitude of reasons in which your system is different from the one where it was developed so it might just not work because it makes certain assumptions about where certain stuff will be or what APIs are available.
Docker eliminates all of those issues because it’s a reproducible environment, so if it runs on one system it runs on another. There’s a lot of value in that, and I’m not sure which resource you think is being wasted, but docker is almost seamless without not much overhead, where you won’t feel it even on a raspberry pi zero.
One of my favorite games to play with my SO is Out of Space the vibe is very similar to Overcooked but it’s procedurally generated and a lot more chilled out, i.e. less chaos.