Open File Locking and Mac OS X?

ArcticMyst asks: "In Mac OS X the responsibility of locking open files has moved from the operating system to individual applications. With the exception of Apple's most recent release of AppleWorks, I have not been able to find many applications written for Mac OS X that will lock a network resident file when it is opened. Not marking a file as locked allows more than one user to have a file open, then edit and save back to the original file. Even most of Apple's own applications fail to do this. Apple does provide information on how to make sure that open files are not edited while they are open. Why do so many applications fail to provide this security?"