I find that the more elaborate the design, the more dated it tends to look after a few years. This isn't always the case but a good example would be the Google logo. It has stayed fairly similar throughout its changes but it has moved to a simpler and more graphic look rather than the "fancy" 3D looking design they previously had. I think the intention has been to move away from the "it's just a search engine" look to something that gives off a stronger sense of credibility.
Also, when a company produces a lot of stuff they need a logo that can easily be used on everything from a tv commercial to a memo to being printed on the side of an airplane. Simpler designs have the advantage when it comes to versatility.