Try that when a stone flies up and hits the end of your lens!
But in general, you have to add and remove the lens hood and anything can happen no matter how careful you are.
A "cheap - in comparison to the lens cost" UV filter just adds that extra protection on the safe side.
Have a read of this, guys http://petapixel.com/2015/08/31/pho...h-do-uv-filters-actually-protect-your-lenses/