It's not that the animals aren't cute enough by themselves, but when their tongues are hanging out of their mouths, the whole thing is even more cute. Unlike humans, for whom it is apparently not nice to pray with a tongue, completely different rules apply in the animal world. Language in relation to a person is a sign of love and not a violation of etiquette or lack of education.
Just think of how many mammals by showing their tongues and licking you, shows affection and emotional attachment to you. They are primarily groomed by licking, because they don't have any combs and brushes, but translated into human language it is about a social act, the act of petting humans by animals. And what could be cuter than that! Maybe only the next photo gallery.