Do Podcasters Need Social Media?
The answer is no. But it can help you do two things:
Connect with people (like potential guests) you wouldn't otherwise be able to reach.
Show your humanity and approachability.
I can't tell you how many podcast interviews I've booked where the process started via a simple message on social media—a public post or response, not even a DM.
For the people you already know, social media is a great way to keep in touch, without having to send a long email, pick up the phone, or get together in-person. It's a no-pressure way to keep relationships moving forward.
It's also an opportunity for current and potential listeners to see how you interact with others. And this "approachability" is huge for listeners liking you—it's right behind empathy as one of the most powerful ways to attract people.
"Followers" on social media are nice, but one-on-one interactions with people you want to meet and current listeners are almost always far more powerful.