No it's more like, they look vulnerable as they aren't wearing a helmet I'll give them some extra room. I was amazed by the extra space I got when cycling with a child seat on the back of my bike.

Wearing a helmet might also might make some drivers drive closer to you and with less care. So it might help make some accidents less severe, but it also might make the chance of a serious accident more likely. It's not as straightforward as many seem to think.