YSK: Cats don't like their whiskers touching their food bowl. This is why they beg even if food is still left at the bottom.
Whisker fatigue causes stress and overstimulates their senses. Using a flat bowl or plate will relieve this issue and allow your cat to eat all their food without stress.
You can also search for "whisker fatigue" bowls specifically made for cats.
I can add my own anecdote to this one. One of my cat's is fine with any bowl because he's just very food motivated and will do anything to get to his food at feeding time. The other one, when using a more narrow bowl, would often stop eating normally and scoop out the food with a paw. Once I switched to wide flatter bowls, she scarfs it down without pause. It was clearly bothering her.
While cats vary in their preferences and tolerances, it bothers me that so many people just scoff at this idea. We're caretakers for cats and should do our best to make their lives as reasonably comfortable and enriching as possible. And just because a cat is fine with touching things with their whiskers in some situations doesn't mean they're cool with it in others. Cats are often happy to have you scratch behind their ears, but only when it's invited.
And come on, bowls are cheap. It's not that big of an inconvenience to get them a bowl that could be more comfortable, even if they're tolerating it now.
So far the only actual study we have on this says it's not a real thing. Sure, some cats have different preferences but it's not like you are torturing your cat with normal bowls and need to run out and buy special ones.
If you're feeding your cat an infinite supply of dry food without a feeding schedule you have bigger things to be concerned about than whisker fatigue.
It's well documented it veterinary literature, you can believe the studies or not 🤷♀️. It's not like it kills your cat instantly, you just deal with diabetes kidney or urinary issues in the future. Not sure why someone would not try to prevent that.
It happens often in media, but real scientists don't rely on what they think animals think, instead using objective data like brain activity scans, heartbeat rates etc, often presenting pure data without a conclusion on what they think the animal feels. Those studies will then come to media, where the interviewed scientists will give their thoughts on how they interpret the results, even if it's obvious that the animal likes/dislikes something. These also exist in media.
Edit: I also want to add that many things are straight up visibly harming the animal and you don't even need any conclusions. For example if you house a hole-dwelling spider without enough substrate to dig, it will stop eating. This has been confirmed many times, by many owners. It doesn't matter if it makes them uncomfortable or they feel pain from it, or they are cold, etc, because we know that they stop eating, and that's a good enough signal that something's bad.