Where I live, and where I bush hog, that cover is handy. It's not only a safety cover, it's also to help keep brush from getting wrapped around the shaft.
In my childhood, I grew up in an inner city neighborhood....BUT my dad had a good friend/coworker who had a farm out in western Nebraska. Big farm. When I was 12, we went out there in the summer and stayed about a week, to get out of the city. We did farm stuff. Up before daylight, outside right at the crack of dawn. We usually took a break in the afternoons. Anyway the farmer's daughter and I took off on the 3 wheelers over to a part of the farm where they were cutting a hay pasture. The farm hand seen us and stopped, asked us if one of us wanted to ride while he was cutting. Sure I said. I hopped up and she walked around back of the tractor. PTO still turning (it was off but still turning). Somehow her shirt got tangled up in the shaft and ripped it right off of her back in nothing flat. She was REAL lucky that the shirt was the only thing she lost. Got a little banged up and red but nothing major happened.
She was accident prone.
Next year, we went back out for a few days and one afternoon we were riding, right before dusk. Headed back to the house. We was riding along me in front, her following. I seen the house and kept riding. Turned around to look and she wasn't behind me anymore. Figured she took the other road to try to beat me home like she would do. Nope. I get to the house and she ain't there. Her dad asked where she was, I thought she was home...anyway, we went back out that dirt road to look for her. Found her. She had rode off of the road and ran into a hay spear. The spear went in under her left eye and was sticking partially out of the back right side of her head, no movement, just hanging there.
y'all need to think about why this stuff is the way it is. Good chance someone had a bad day at some point, which led to some kind of safety device. You wouldn't believe how many people bypass safety switches-especially seat switches-on mowers and tractors. Think about it. You're bush hogging, run up on a tree or log or into a hole that you didn't know was there, you get thrown off, and if that machine doesn't stop, it won't. Your body sure won't stop it. But if that safety switch works, you have a better chance of not getting bush hogged, baled, disc'd, plowed, or just run over.