If you were trying to talk to someone, trying to engage them in any kind of a meaningful conversation, you would expect them to make and maintain eye contact with you throughout the experience. That expectation is a normal cultural assumption, but it is also a visceral behavioral response that goes far beyond words in meaning. Establishing and maintaining direct eye contact (without the challenge of a dominant glare or staring) is behavioral verification of respect for another entity, or another person in terms of the human realm. If you were trying to converse with another person, and they deliberately went out of their way to not look at you or they even passively refused to look at you, as they continued to talk to you, over any period of extended time, your correct perception would be that of their disrespect, apathy, and/or avoidance. It is quite easy to see and understand the inherent behavioral truth in such a display of action.
The same applies, just as directly and profoundly, to having sex or making love.