A couple of really good uses for a lens hood that only become apparent when the need jumps out at you.
First it protects the front of the lens from bumps, scrapes etc. Some people like glass filters to do this, some don't. I don't. Personally I always use a hood, but that is a whole other debate.
Second, ever drive east about an hour before sunrise or west about and hour before sunset. The sun that is shining indirectly into your eyes making it harder to see is the same kind of thing that light in front of the lens will cause producing lens flare. A hood can help reduce the likely hood of lens flare.