I must say that sleeping humans are not that cute (with the exception perhaps of baby humans.) They are twisted and have messy unmanageable hair and bed-clothes and sometimes thrash around. Indeed humans do not wish to be seen sleeping, nor to be seen waking up in the morning without a substantial amount of time spent to make themselves presentable.
Not so with cats. All cats have a particular expression of joy while sleeping and are very pleasant to look at. Their soft fur stays nice and intact at all times and the feet are particularly cute. Here are some examples.
Tiger is 8 years old and still enjoys sleeping very much.
Not all cats sleep the same but they all sleep cute. Here is Benji sleeping. He is not quite one year old.