pups, cubs and kittens

[maz]

Why are the young of big cats called cubs and small cats called kittens, when all varieties od dogs have pups?

[wildwood]

An interesting observation I hadn't thought of before.
Perhaps because cats - lions, tigers, cervals, moggies etc. - are quite different species from each other. All varieties of dogs are one species. Young of the african wild dog, also a member of the canine family, are sometimes referred to as cubs.