There tends to be less of a problem with non-compliance with prescribed standards of dress on longer cruises because longer cruises tend to draw passengers who have taken enough cruises to know what's expected of them.
There's more and more problems
with people following the suggested dress codes because the cruise line takes no initiative to enforce their own rules of behavior.
I think it's also likely the case that they don't because they see the movement of passenger requests is toward more relaxed dress structure.
Frankly I think anyone who believes Celebrity passengers follow the suggested dress codes more than any other cruise lines is kidding themselves.
I personally like a couple of formal nights to change the ambience of the evening... but the majority of paying passengers of late seem to disagree.