You’ll notice it says shouldn’t, not can’t, in the title. If you have the youthful looks and/or physique to pull off any of these items, by all means wear them (at your peril). Some people have a strong sense of style and know what works for them*. That being said, I think when you cross the 30 threshold you should take a good hard look at yourself in the mirror and think: ‘I’m a man’.