What's There In An (Extra) Name

There are two twins in my apartment complex. Today they were cycling. 

They look identical, have the same height and their names are almost identical. One is Advita and the other is ... I forgot. Something very close to Advita.

I met them and told them that they have the same look are equally tall, have similar bicycles, dress the same way, they should have the same name TOO. They looked at each other and then pointed out the obvious flaw. Advita said to me "if our mother calls us then we will BOTH have to run to her, if we have the same name."

I asked them. Does their mother EVER have the need to call ONLY ONE of them for anything? Maybe for dinner or to buy a badminton racquet or colouring pencil? The two girls slowly shook their head. They said their mother always calls both of them.

I pointed out to them. "WHY DO YOU THEN NEED TWO DIFFERENT NAMES?. You are wasting one name." I suggested that they talk to their mother and get rid of one name and use the other for both of them.

I am waiting to see what their mother has to say about my suggestion.