I answer the door if I'm expecting someone. Friends will call or text on their way over. Or, I just hang out outside and wait for them because most likely they're coming over to have a dog play date or train.
But, if someone comes to the door while I'm home without Mr. Boats...I just let them knock. I work from home, so I am usually around during the day. The only people who knock on our door is someone trying to sell something. I just let the dogs bark. Our front window is such that I can catch a glimpse of someone standing there so I can get an idea if it's someone I want to talk with (9.9 times out of 10...it isn't.)
Earlier this year, there was a string of break ins in RI where burglars were posing as "town workers" and forcing their way into homes when women answered the door. That's the other reason I don't open the door. Yes, I have two Rottweilers and God help anyone who comes in here unarmed to do harm. But, I would rather just not even tempt that sort of fate...so the door stays closed.