The costs have ballooned too much. When seasons were 18 episodes and it costs $100k per episode, it made sense to serialize. Often they were written as they were filmed. Now every episode costs $10 million and preproduction takes a year before the first scene can be filmed with massive post production. No one has really cracked the formula for making TV formats work well on streaming services. The all at once for binge watching only works if you already have a massive archive of shows to expose. The one episode a week for short boutique series that run a season every 3 years is not working well either.