Whilst away on vacation recently, my lovely neighbour agreed to look after the cat and house - however, after seeing a lifesize Frankenstein's Monster upon walking in on the first night, and almost having a heart attack, she refused to come back at night without her husband. I really should have warned her, I suppose.
So yes - some non-prop people really DO find them creepy in a home environment, there's no escaping the reality of that.
But when you've worked on displays for a long time and modified or built mannequins, you become completely desensitized to them, of course. They just become big display stands for cool stuff, or big action figures.