Why are there fees for delivery of technical items to residential addresses? -

I run a business out of my home. I am a retired scientist but active consultant and inventor. Big chemical houses won t do business with me because I am working out of my home (can t afford a private lab), so I order through friends. I need to order electrical sensors and non-chemical supplies for a project, but I will be charged extra because delivery is to a residence. Why is this - my money is as real as IBMs? I am not making drugs, legal or illegal.I appreciate responses.

One reason I ve heard articulated is, depending on the vehicle, it is sometimes difficult to get the truck through narrow residential streets, there is no loading dock, bigger chance that someone is not home to take delivery so they have to reschedule. Things like that.