system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it considered rude when you reject someone offering you food/beverage in their home?

I install ac units, so I'm working in someone's house everyday.  I have noticed that this doesn't not happen all of the time, or doesn't not seem to be any specific type of person.  

But why is it considered rude?  At times, even when I sincerely thank, but deny someone's offer, they seem to be a little hurt or irritated.  

Thanks in advance Reddit!  

Edit:  thanks for all of the responses guys!!
gpt
warning: i am going to make blanket statements and sweeping generalizations in the interest of keeping this brief.

when you see someone working on your behalf you want to help them somehow. even if you are going to pay them you feel like you should be doing SOMETHING. holding a flashlight, handing them nails, something. you see they are sweaty, they might be thirsty, so you offer them a beverage, just something to help. and then they reject it and you find there is NOTHING you can do to help, you feel powerless, helpless, worthless. this guy is fixing something you broke and you can't even help him with his thirst.