I always use a UV filter, and always have (unless, as with the Nikon 14-24, it's impossible).
When I was in the field in the South Pacific, for example, I had mud, dirt, rain, pig snot, blood, dog sneezes, sap, clouds of insects . . . all liable to be flying around when I was shooting. The filters made it easy to clean all this crud from the front of the lens. Better to clean a filter with what's on hand, sometimes just a t shirt, than to try cleaning the front element of a lens. If you mess up the filter, put on another one.
And even here, where I lead a more restrained life, I routinely get into situations where stuff's flying around.
What I'm saying is that "protection" is more than just keeping something from damaging the lens. Sometimes that filter makes it possible to keep shooting.