I never answer my door for people I don't know. Heck, I don't even answer it when my friends come over. I just yell from my living room for them to come in. When Purolator delivered a package one time I didn't answer. They leave a pickup slip, so I just went and picked my package up at Purolator. The only time I'll answer it, and I kinda have to, is when the pizza guy delivers pizza.
Conclusion....I'm just really lazy.