I have a battery electric lawnmower. I found I got noticably better battery life after sharpening the blade to a near razor edge. Yes the edge is more fragile but it cuts the grass with much less resistance.

That I did not know. I still wouldn't stick a finger near one of course.

They still work when blunted which is most of the time. But ideally they are sharp and slicing pure grass, grass tolerates slicing better than ripping. It's like a sword, ideally it is razor sharp, doesn't chip when blunted, and still works as a decent club even when blunted because it will be the second it hits something hard.

For regular mowing sure. For reel mowing (e.g. golf) you will want to sharpen them.

They are meant to be sharp like an axe (high angle), not sharp like a knife (low angle). They aren’t supposed to be blunt like a butter knife. Dull blades damage the grass.