My mum lives with us, is in all day and takes in parcels for the whole street. She has a lovely chat to the delivery drivers (she knows them all by name now) and the neighbours are always grateful. She's been having cancer treatment this last year and the response from our neighbours has been wonderful. It's all just part of living in a community, isn't it?
Get your point that you are working, my Dad was self-employed for many years, but you have to be proactive; you can't expect delivery drivers to know that. Put a sign up saying you are working and not to be disturbed. There's no point whinging about being disturbed if you won't take even the most basic step to stop it happening. I'm sure most people would specify, if they could, a time when they would be home for parcel delivery, they're not trying to annoy you specifically.
I think you like being disturbed really, it's a distraction from work and then you get to impress your friends with your martyrdom by exaggerating lying about how many parcels you have taken in. 