I voted "occasionally". Not often, not all the time - just occasionally, at some point in time during sex ...
Answer to the question "why?": because you can, I guess. All there's to it. Even if you're intensely involved in what you're doing and what you're feeling, your imagination always is at work to add elements and possibilities and everything we can think about ... involuntarily, I guess. Sometimes not: you're just all there, feeling every touch, every brush of the hand, every touching of lips, every move and every sensation of the skin. But like you said - sometimes your imagination adds the fantasy about being
somewhere else - or in another situation ... you imagine delicate or daring variations of what you're doing right now, and it makes it all feel even better ... and sometimes, you add a person in the mix, even perhaps just
besides your partner. I dunno ...
Not that I´ve
had any in the past couple of months ...