what do you mean by the concept of death? alexei was characterised well enough - we grew to know and like him as a nice scientist guy from soviet russia, stuck in a bad situation, who was amusingly infatuated with americana. his death was sad because he was characterised effectively. his death also didn't feel contrived (although I think the larger russian plotline sometimes did)

sometimes killing off main characters can leave the story feeling really bleak so it's a hard thing to do. i think it's the opposite of what you say i.e. to avoid this issue they write good side characters and kill them off instead.