I really can’t say it any better than this:
Now let me make one thing absolutely plain. Dress codes are for the terminally stupid. Telling your guests what to wear implies that a) you are a megalomaniac or that b) you’ve invited such a bunch of witless fools, they’d all turn up in bearskin hats if left to their own devices. I simply will not go to any establishment that requires me to wear a suit, or a tie.