This kind of thing only works when a game is just coming off of launch
(although, i dont know if smite's is actually still avaliable)
in most cases, the game offering the bundle of every character forever only has a very small roster at launch, so the total worth of the bundle is actually relative to what it would cost to get each character
if league were to put one out now for say, $30 or something, the actual amount to buy each champion now is absolutely not worth it for Riot to sell them and all future characters for that much
its meant to draw in players and keep them invested in a game's early stages so it can grow
almost always as a limited time sale, or a "Founder's Pack"