Content gets you in front of people who do not know you yet. A post, a video, a comment that shows up at the right moment.
Email does something different. It keeps you in front of people who already raised a hand: downloaded something, asked a question, then went quiet.
Most businesses only do the first one. They post, they wait, and every lead who does not buy immediately disappears into nothing.
The two work together. Content brings people in. Email keeps them warm until they are ready to buy.