What's movies, novels and dramas all about? Story? Are you an idiot? Character! from which everything is flown.
Then what's character all about? Providing history and uniqueness. When you know some history of her/him you know her/him. When you know her/him you are forced to have sympathy for her/him. If you provide a character with history and uniqueness however the character is cruel or nasty s/he can get readers' sympathy, meaning the readers are being under your thumb. It's the secret of great writers and the holy grail of dull ones.
Above clip is from "The Hour", a British-born TV drama, which is impossibly sleepy and extremely naive as usual. For example something like "Have you had a single original thought in your life?"(00:58~) line. But I like it!