New column modifier?

I am wondering about useful something might be. So I hope ya'll don't mind me throwing out for feedback. I am fairly good with standard SQL, but not the more advanced DBA things such as TRIGGERs. I am reading good book, "PostgreSQL Server Programming" to increase my knowledge. The section that I'm on now is about triggers. And how to use them to enforce a "read only" column. So I'm wondering if such is very common? I can see some uses for it with things which "should not change", such as a system generated date/time in an audit log. Given how much PostgreSQL extends beyond the ANSI standard, I'm wondering if a new column modifier, perhaps "WORM" (Write Once, Read Many) might be of any real use. Or is this "need" just not prevalent enough to require such a thing?

just thinking. But maybe not productively.