If you do lots of turns, you'll know what's going on around you.
I turn rather more than average
when space allows. Space doesn't always allow, though. One thing far too many leaders forget is that followers are three-dimensional. If you lead them in a turn, they have to go somewhere . . . and it's easier to judge whether there's space if you can see said space, which can be tricky for turns to the right if someone's head is there.
Some of us (me) don't sweat much.
I run very, very hot. Two to three shirts per milonga even with breaks, water, and antiperspirant.
Dancing cheek-to-cheek feels real nice. What's the big deal? You're already dancing boob-to-chest. Try cheek-to-cheek for a song.
It's really not about issues with body contact. I just like to see where I'm turning.
It's hard to move your head when you've got face-to-face contact, but you can still move your eyes. So, turn your eyes left when you turn left. And, if you can see over your partner's head, turn your eyes right when you turn right.
My eyes can't deflect more than the typical 60° of most humans. Whereas as part of my turning, I often use rapid 180° enrosques, alteraciones, etc., not to mention circular colgaditas. My partner is a very fast stepper, for which I'm thankful. So, to put her in the spot which is currently behind my head, I need to know there's space for her there . . . If someone is there, I can react quickly enough if they're at the edge of the field of vision that using my
neck and eyes affords me, but not if I wait until my
eyes alone pick them up.
Anyway, this sounds stylistic. I'm not a fan of the romantic, slow, walk-and-rock style of tango. I prefer to dance very dynamically, using rapid direction changes and sharp pivots to express the music. That's hotter (more movement) and demands more visual scanning. It's just my preference. I've tried dancing other ways. I find it boring.