Seems that bikes, having 2 wheels, tend to be unstable things, unlike trikes, and gravity and wind affects unstable things in unpredictable ways. They've an annoying way of waiting till you're not looking, then escaping the tree or curb or park bench, and crashing to the ground while grinding hard bark or concrete or steel bench frames along those wonderful graphics on your tubes which aren't so wonderful anymore at that point. All that hits the ground when I lay mine down is a pedal end and some cheap handlebar tape. I never lay it down on concrete. I'd rather replace 3 feet of bar tape than to have to order new Velocals and repair a scraped frame. The pedals? Their on their own.

The "rather safe than sorry" thing comes to mind.