I don't answer the door.
Simply because we live too far from friends and relatives so we always know in advance. And besides, my living room looks out onto the car park area too - and visitors always park along our windows (because we're at the end of the car park - far from the entrance gates).
So there's no need for me to open it in 99% of cases.
It's always religious botherers (unwelcome), sales people (unwelcome) etc.
In the whole time I've lived here (4.5yrs) I've rarely opened the door, and the times I have, it's been a waste of my time.
So why would I get up off the sofa, stop cooking dinner, make someone I'm on the phone to be on hold, put down my book, get out of th bath for... or whatever?
No incentive here.
However, DH doesn't open the door either. So there we are!