It's all to do with the type of crowd they want inside and the type of people they want in. Places like Reds, EC's and a few other places are shocking for this.
I get refused entry weekly into Reds because all my mates look too much like bikies/skin heads/have too many tattoos/beards don't look right/etc. I just line up each week as a joke now because I love hearing their excuses (not the right shoes, not the right shirt, offensive facial hair, too drunk, etc).
If you want a place where you're garunteed to get in no matter what you're wearing or what state you're in, hit Club 58. It's where all the people who get refused entry into Earth go.
HQ is pretty good about dress code these days. They let most things slip by, except visable tattoo's due to club related stuff, but a few of my mates just cover up and they're let in fine.
The key is, just have 2 or 3 lovely ladies hanging off your arms, then line up for a place. You're garunteed to be let in. Works every time for me even if I can't even get my ID out because I'm too wasted.