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. - eviltoast

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.

More info