Only a small minority of animal species have common names. Common names are given to animals that the general population is familiar with. Such names are not assigned by scientists. Most of the known species of animals are not familiar to most people, and therefore never have common names assigned. General categories of animals may have common names, like "beetles" or "sea urchins" for example. But most individual species of beetles and sea urchins do not have common names, because most of them are unfamiliar to most people other than zoologists who specialize in such groups; and zoologists refer to all such species by their scientific names. There are hundreds of species of fleas, hundreds of species of ticks, hundreds of species of leeches, etc., very few of which have common names.
I specialize in marine molluscs. Molluscs are more familiar to ordinary folks than most invertebrate groups because a good number of people collect seashells, and shells are familiar in crafts, gift shops, tourist shops, jewelry, etc. Yet, probably fewer than 5% of the 200,000 described species of marine molluscs have common names assigned to them, and even shell collectors use the scientific names.