Breaking changes are scary for running solutions. it is why IT has a mandate of "Never touch a running system" (security patches only)
Immich is a younger, quickly evolving project, so new features or improvements may justify breaking the upgrade path. There may be folks that share data migration tips when that happens.
It is why in corporate world we never want to be on the latest version of something; let the non critical data users find the problems.
Also you may have seen this on the project page. Basically use at own risk until things mature:
⚠️ The project is under very active development. Expect bugs and changes. Do not use it as the only way to store your photos and videos!