Might pay to mention your model drone, some hoods cover more / work better than others from what I've seen here.
I've never had one, but my take on them is yes they may protect from impact in the event of a crash, and with a minor impact one could make a difference.
Most damage in all but a minor incident would be the g-shock received though, and a hood would not help much.
They will reduce les flare a little from angles they protect from.
I've seen post here that have noted when turning, pitching etc, the edges of some model hoods can be seen briefly, and to fix requires a little (dremel or such) sanding down.