I've witnessed lots of young men in particular shovelling food while hunched over their plates as well. It turns by stomach. Also I used to live in a country with a very different culture to ours and I noticed that the women in particular would put HUGE lumps of food into their mouths and then chew with their mouths open, probably because they struggled to cut their food up into bite size pieces.
I've noticed in recent years that so many people seem to struggle to hold cutlery properly. I'm sure it didn't used to be like this. They are often white and from a western culture as well, so it's not as if they haven't grown up being accustomed to knives and forks.
I am not a complete snob about it, I don't think there is only one 'right' way, I don't care if you use your fork like a scoop sometimes, or whether you hold it facing upwards or downwards, so long as it works and doesn't look massively awkward, sloppy and inefficient. But these people don't seem to be able to manage their cutlery at all. They hold it in the most bizarre ways and seem incapable of manipulating it to perform the function it was designed for. No disabilities such as arthritis as far as I can tell. It's something that seems to be an issue with increasing numbers of young people and I don't remember knowing anyone who ate like this when I was growing up.
I know several people in their late teens and 20s who grip their fork like a spear and then stick it into the food while holding it completely upright, like they are putting one of those flag poles into a golfing hole, if that makes sense. Then they tear and drag at the food with their knife rather than cutting it or sawing at it.
When I was in the States I noticed this more than ever. Lots of very odd cutlery holding styles, balancing forks and spoons across three or four splayed fingers of an upturned hand, or gripping it like a javelin they are just about to throw.
I know Americans like to cut their food with their knife first, then put it to one side, switch their fork to the other hand and just eat with their fork. I don't claim to understand it, but it doesn't bother me.
What does bother me is when they get too lazy to switch back to their knife as needed, so they try to cut their food with their fork. They spend so long hacking and sawing away at their food with the blunt side of their fork and I want to scream 'just use the bloody knife for God's sake! That's what it's sitting there for, remember?'