Sounds like an evolutionary explanation, or part of it anyway. We produce and radiate heat that is mostly wasted, so shared bodily heat like you said does make

Sounds like an evolutionary explanation, or part of it anyway. We produce and radiate heat that is mostly wasted, so shared bodily heat like you said does make sense from the point of view of physics. At the same time letting someone close enough to be able to mutually benefit from heat (and get cozy) is possible when there's mutual affection.