The original question was what can he expect if he goes without a filter and a hood. If we lived in a perfect world, nothing bad would occur, and things would be fine.
In the real world, expect fingerprints on the front glass when you try to change the aperture and one of your fingers ends up on the glass instead. Or, a handprint when someone doesn't want their picture taken and starts shoving your camera into your face by applying palm pressure to your lens.
Expect people to cough, laugh up their food, expectorate or vomit on your glass. Expect that when you try to clean up the goober from the above you'll scratch your front element. Expect that anyone spray painting or sandblasting nearby will leave residue on your front glass.
When you change lenses, expect that you could drop it, front element downwards on some nice jagged gravel. It's easier to replace a broken UV filter than a cracked front element. But, it's your money.
In case you think that these things couldn't possibly happen, they've all happened to me at one time or another. You don't have to be taking photographs in Afghanistan either. Just try taking pictures of your babies when they're eating and you'll know about the spitting and expectoration. My baby had the stomach flu yesterday, so he's been having projectile vomiting. Check!
I've happily thrown away shattered filters and put new ones on.