This is an excellent thread, so i'm bumping it up, someone should make it a sticky...
I'll go ahead and make a sticky with some of the links in here, I agree with you.
The primary purpose of the DATA statement is to give names to constants; instead of referring to pi as 3.141592653589793 at every appearance, the variable PI can be given that value with a DATA statement and used instead of the longer form of the constant. This also simplifies modifying the program, should the value of pi change.
-- FORTRAN manual for Xerox Computers