Your choice of dress depends on both your age and the environment you're in. I definitely wouldn't wear trainers (sneakers) to work, but equally I also wouldn't wear anything other than trainers to certain clubs. It's very easy to look over-dressed and pretentious if you're 18. Equally it's very easy to look like an idiot trying to wear teenager's fashion if you're 30 and cruising about in high tops.

I absolutely agree that fit is crucial for clothes. However, everyone has a different context and you really don't want to look woefully out of place. Sometimes that means wearing (nice) trainers.