It's not impossible to pull out if you draw well and, more importantly, your opponent draws poorly (a poor selection of attacks/not enough resources to play multiple attacks/non-attack cards drawn/ect...), especially with decks that have a more varied selection of cards. With Kassai it's tougher because she is so consistent in her attacks/cards and as such almost never gives a break when closing out a game that gets to this point. Other decks might stumble and let the opponent start making attacks of their own (maybe leading to it going the other way if both are at low life). Still the endgame spiral of tossing your hand to survive is a real thing and if you don't want to play it out you can concede. It's your choice and I wouldn't consider it bad manners at all.

I’m new so I came to ask the same thing.

That’s part of Fai’s ability. It allows him to start with one in his GY at the beginning of the game