Short answer: A genetic deficiency prevents cats from tasting sweets.
Other than cats, every other mammal (including humans) examined to date can taste sweetness. This is due to us having five types of taste buds. We can taste sourness, saltiness, umami (meatiness), bitterness, and sweetness. Now, this doesn’t mean that we will all enjoy the taste of sweets, but we all have the “wiring” to taste sweetness. Why are cats different?
It has been known for years that cats pay little attention to all things sweet, but no one really knew why. In 2005, scientists from the Monell Chemical Senses Center in Philadelphia discovered something interesting. Cats have a genetic deficiency that essentially deletes the sugar detectors on the taste buds of cats. In other words, cats do not possess the “wiring” to taste sweets.
There is a small percentage of cats that will actually eat sweets. This doesn’t mean that they can taste the sweetness, though. Cats that eat sweets might be doing so because they are attracted to the bitterness, saltiness, amino acids, texture, or possibly just the smell.