While primordial pouches might make your cat look like a floppy idiot, they may actually be serving some pretty badass purposes:

Protection: famous for their “bunny kicking” abilities, these pouches provide an extra layer of fat and tissue to protect the cat’s vital organs from sharp claws during fights and playful roughhousing.
Flexibility: cats are able to extend their bodies to perform impressive jumps of distances approximately five to six times the length of their body, both vertically and horizontally. This extra skin allows them to take longer strides, leap further, and twist their torso to land on their feet.
Food storage: while domesticated cats tend to prefer their food little and often, many breeds haven’t physically evolved far from their days as wildcats. In the wild, cats may gorge on a large meal when food supplies are limited, and these pouches allow their bellies to expand to accommodate these larger meals.
Heat regulation: some also speculate that the pouches enable better air circulation that aids in temperature control; however, these are all still theories as experts remain unsure of the true purpose of the pouch.

[iflscience.com]