The base system and packages are usually smaller than home, so the possibility of a bitrot is actually lower. Package files' integrity can also be automatically

The base system and packages are usually smaller than home, so the possibility of a bitrot is actually lower. Package files' integrity can also be automatically checked by some tools. In addition, they are much easier to reproduce, as you said, one can always just reinstall the system and download all packages again. Your home and /etc actually matter more.