They started as a designer luxury faux fur throw. but seemed to evoke an emotional, faux-parent connection for cats. (likely too for other pets)
Most pets can be immediately comforted by a KNEADIE; the faux fur reminding them of their mother's fur.
In the 70's, psychologist, Harry Harlow, experimented by pairing 'pretend-parent cloth monkeys' with actual baby monkeys to help prove the emotional connection between parents and infants.
I've provided a further link to his findings on my Blog Post 'Gifts For Pet Lovers