I get to wear a suit a good bit at work too, and don't just love it on vacation, but we have been on 2 7 nights on the magic and it semmed like there were more dressed up than not. Now there were probably only a couple dozen tuxes, but most had on a jacket of some kind, and several military dress. Now we have always been second seating as well, so i don't know if that matters. I may get the big flame of death here, ( i will even flame myself if that helps) but I don't understand why so many people try to do the bare minimum for things.
DCL sets it as a formal night, puts the requests in writing, and trys to keep it as a "higher" class evening and ship for that matter. I fully understand that not everybody has money to go buy a new outfit just for the one time they will wear something on the cruise and that is not at all where I am going with this. But just because they will still let you come into the dining room and eat, serve you as well as everyone else, does not mean that I think you should show up in flip flops and t shirt, even high dollar nice ones that cost more than some dress clothes. That being said, I take a suit and a couple of shirt tie combos. Last time i did not wear the tie for semi formal night, but did wear the jacket. And i am another that really likes the formal atmosphere of everyone being dressed up for the evening, kids, parents and all together. It just helps give some of that feeling that makes up exactly why we cruise on disney and not some of the other with no formal anything.