I was reflecting on the fact that, at least in Western culture, most children are taught at a young age what sounds animals make. However, this is mostly a "useless" information from a practical point of view, especially so for a child - so I wonder, are animal sounds taught because it's just a cultural habit or does it have a purpose in the development of the child?
According to a speech therapist of one of my young relatives, the animal sounds that we commonly teach children contain many of the most common English phonemes combinations in short, approachable words. There is also an aspect of toddlers often being fascinated by animals, so it's a motivating and fun way for them to practice these important sounds.
I've read that a child will often learn to vocalize the sound an animal makes before they will actually say the name of the animal. For instance, they are more likely to say "moo!" when they see a cow, before actually saying "cow!".
That said, my daughter says dog, duck and kitty at 15 months old. No woof, quack or meow.
Imitating animal sounds is intuitively a great way to introduce spoken communication. Language is tough to get started with for someone with no point of reference at all, and almost all words are pure convention. If you both look at a cow and you say "moo", however, the connection between your use of spoken language, and the object of your shared attention is more obvious, whereas "cow", for a non speaker, could be referring to the grass, the color of the cow, or a crow on its head, if indeed they even realize that in producing speech sounds, you are performing a task of labelling what you see.
Small children generally show great interest in animals, too, so all the more likely that's where there attention is. If they've heard the cow say moo, they might get that you're naming it, and you've had a successful spoken communication. In which case you may just have taught them that language can do that in the first place, and you may have set an interest in motion.