In the Finder, Outlook Express, Netscape Communicator, Internet Explorer, Adobe GoLive, many other applications, and recently Word 2001, a Preferences item is under the Edit menu. The Edit menu seems to be a de facto standard. However, it is not that simple. I just mentioned that Microsoft Word recently moved the prefs to the Edit menu, because they used to be in the Tools menu. The Settings menu item probably outlives my years of Mac experience, but now breaks a de facto standard.
Some applications impose radically different methods.
I have used it since version 4.0 and it is the way I always had to access the preferences. As if this was not enough, Mac OS X migrates the preferences standard from under the Edit menu to the new application menu. It is easy to ask yourself whether we need standards, ever-changing standards, or no standards at all. That concerns a mundane menu item. Extend the inquiry to important matters and you have a difficult subject to examine.