What if it was your OWN money you'd fumbled and dropped ?
Surely you wouldn't just walk off and leave it, thats almost littering. I'd certainly stoop to pick up my own 5p, but I might be a bit embarrassed.
Coppers can DO one though. Sorry Edna.
What if the 5p has fallen on the slippy type floor you get in many shops, they can be a bugger to pick up. You may look a right SPACKER trying to push that 5p around trying to get your nails underneath it. Boot it away and look cool instead I reckon.