Netflix’s decision to launch an advertising-supported version is a risky move that flings the giant into a business it has resisted for years. But the push—scheduled for next year—has one thing going for it: Advertisers are thirsty for more ways to reach people watching streaming TV and movies online.

Cord cutting has left brands with a supply-and-demand problem. As broadcast and cable viewership diminishes, traditional TV advertising isn’t reaching as many people, and networks are packing in the ads to avoid steep revenue declines. But streaming services like Hulu, Roku and HBO Max are selling ads sparingly so as not to alienate watchers.