for me it's
* showing of my legs while being able to highlight the top of my body in a more flattering way than any T-shirt might allow
* not having to deal with ill fitting off the rack pants that have to be readjusted ever few minutes
* speaking of which, I always feel like dresses have a broader range on what cuts fit
* if I'm in the mood for a dress - I always feel like I'm looking good in them. Not much more required than putting it on. Instant fabulous feeling