Why are Linux file permissions so primitive? [closed]

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http://stackoverflow.com – Why are Linux file permissions still so primitive and is this likely to ever change? Each file/dir can only have an owner and group. This seems to make the following things extremely difficult to implement: How can you make a file read only and not delete-able, but still give that user permission to write to its directory? How can you restrict directories to only certain users with out having to create a group for every possible combination of users required? And having done that its useless anyway because anyone who creates a file doesn't get it's permissions inheretted, so every user has (HowTos)