Naming using a fixed set of rules is important so that all compounds are recognised globally by the same name to avoid confusion and misunderstanding.
Compounds are named so as to distinguish one compound from another. At times the chemical name of a compound is very long and so to communicate better,a common word/name is used instead. Compounds have a common name, a proper name and a chemical formulae. For example:
Common name: water
Proper name: dihydrogen monoxide
Chemical formulae: H2O
Chemists may use any one or a combination. Some times, it is simply more convenient and safer to use the common name so that even a child would understand what water(H2O) is and not accidentally ingest bleach(hydrogen peroxide/H2O2).