Social media is usually lumped in with digital marketing, as if it is all the same stuff, part of the same marketing toolbox.
There is some overlap, significantly around the advertising that occurs on social platforms, but not as much as most just assume.
Think about being at a party, the bloke in the corner holding forth to a small group of people, arguing a point of view, taking questions, and debating the foundations of his views. The person on the right is not talking, not asking questions, but they are listening.
Are they engaged in the conversation??
Of course they are.
Do they want to be sold to?
Probably not, they are just listening, at some point of they want some clarification, to actively instead of passively engage in the conversation, or to be sold to, they will ask a question, make a comment, or otherwise change their engagement from passive to active.
Social media is the same, a few people are engaging overtly, liking, retweeting, commenting, sharing, and so on, but those “listening” can also be passively engaging, absorbing the flow of the conversation, and they matter.
By contrast to social media platforms, email or digital marketing takes a message, information, or a sales pitch and sends it to you, expecting an outcome, one of which can be that you ignore it and perhaps unsubscribe.
The response rates to email marketing are way better than stuffing letterboxes as we did in the old days, which delivered 1% if you were really lucky, had a great offer and a good copywriter, simply because it was almost random. The best you could do to profile the potential customers was broad brush demographics of the location of the letterboxes to be stuffed.
Email or digital marketing however can be hugely more effective, as you market to a list, people who have expressed some interest in hearing what you have to say, and which you can slice and die in all sorts of ways to have a highly targeted and personalised communication that offers the option to becoming a conversation, at the initiation of the receiver.
The other point to remember is that everyone influences someone.