I've never kicked cans, but I have kicked pebbles down the street while walking home from school, and I used whichever foot was closest to the pebble. Consider this: if an object is directly in front of your left foot (by however many inches) it is MUCH easier to kick it with that foot than to try to kick it with the right foot. I mean you CAN, but then the object will go sideways. The only way the object will go forward is if you twist your foot/leg and that's really too much effort, if you ask me.
I'm sure the director wanted the incident to look natural. If the director had told Teri "you NEED to kick it with your right foot" then she'd have been concentrating on making sure her right foot was in the correct position and she'd be focused on her pacing and not so much on her lines and would it really have been worth it?
...eh, who knows. But good observation & welcome to the MBs.
