Apart from that... Well, the thing is, WotC doesn't want people to just try adventures with no commitment. If people play a short adventure they quickly reach the end. And that leads to a "Well, that was fun. Goodbye everyone" moment. If you play a campaign, even just planning on showing off people the start, then there's the incentive to keep playing. It's easy to keep playing. If they don't like it, then the fact they're walking out on the story doesn't matter. If they're curious enough to keep playing and the story isn't over, that keeps them coming back! Which moves people from playing D&D as a one-time game night thing to regular players.
It's a Scheherazade situation. If you keep ending on a cliffhanger, people will keep listening to the story night after night.