Typical phone conversation on the WMATA

"Hello?"

"Hello? It's me."

"Hey, how are you doing?"

"Can I call you back? I'm on the metro."

"Hello? You're breaking up."

"Can I call you back? Hello? Hello??"

"I am on the metro!"

*call disconnects*

If people know that the calls are going to be disconnected while they are on the metro, what is the purpose of picking up the call in the first place?