I've found that many developers are reluctant to use "new" features like CASE expressions and ANSI joins. (By new I mean: this millennium.)
But now they have started to and they get carried away. I have seen this several times recently:
CASE WHEN column1 IS NOT NULL THEN column1 ELSE column2 END
Before they learned to use CASE I'm sure they would have written the much simpler:
NVL (column1, column2)
Now I now that NVL is Oracle-specific and CASE is portable, but (a) we aren't ever going to be porting our millions of lines of PL/SQL, and (b) I can guarantee they didn't do it for that reason. They have got a new hammer and now everything looks like a nail.