One of the most important behaviours you can teach your dog is to "wait" at the door until released. The purpose is simply for good manners and for safety.

I do not step through the door before my dogs to show them I am "dominant". That is a common myth. I go through before simply because I want to make sure there are no squirrels or other distractions that may catch my dog's attention. 

There are times my front door is open and I don't release them to step outside. I may be watering flowers or picking up a newspaper or speaking with someone at the door. Waiting calmly for a release signal is a great real life reward. 

Dogs need to learn an open door is not an invitation to step out.