Agreed, I have yet to sail on any ship be it for a 7 night cruise or a short 3/4/5 night version that they had a formal night on the 1st night. Because luggage delivery can be delayed (especially if it's harboring alcohol) the first night of a cruise is classified as resort casual and I have even wore jeans to dinner that night- never shorts though.
The captain's dinner which is the major formal night is the 2nd night of a cruise and if you hate wearing tuxs, gowns or cocktail dresses then their are always other dining alternatives. Don't feel pressured to dress up..it's your cruise.
Just an FYI Disney's ships do not do any sort of formal night for their short cruises. Most people wear business casual aboard their ships for dinner, but they do allow jeans (no shorts).
Last cruise...Disney Dream 4/2011 Next cruise: Allure 5/27/12 (Platinum Members)