I sure as hell don't clear the snow behind my vehicle if I am pulling out forward. If I am backing out yes, but if I'm not driving through the snow behind me, why should I waste time and energy clearing it? I would even go so far as to say if there was snow on the sides of my car and I had to back out, I would only clear the snow behind my car and not on the side(where my exhaust happens to go).
I guess laziness would be a factor in all of this. Here's my snow clearing ritual:
Cut a swath to the door, brush snow off door and window, including that 'overhang' from the roof. Jump in, close the door really hard in hopes of creating a mini-avalanche around the rest of the vehicle; every bit helps. Start engine, rev it up a little, crank heater/defroster on full. Get out of vehicle, you can hear whether the tail pipe is obstructed by the extra back-pressure, throatiness, or 'ping' in the exhaust note. If tail pipe is obstructed, run around and brush snow away from tail pipe.
Start brushing snow away from high to low; roof, support pillars, driver and passenger windows, windshield, free up wipers and clear solvent nozzle, horizontal sides of the roof and trunk lid, mirrors, then all the way around the car, including the headlights and turn signals. If I wasn't going to back up, I may not clear snow completely away from the rear side of the vehicle, but I would certainly go back there in any event to clear off the rear window, brake lights, and license plate.
And I'm always doing this with no hat, no gloves, a light jacket, and tennis shoes. I don't own a hat or pair of gloves.
There was a guy on the news last night shoveling snow in shorts. I've done that, too.