NO THEY DO NOT!
In fact, if you are a relatively unknown author, a “traditional” publisher might not even take you on without a significant number of followers (either on one of the social media platforms or in the form of an email list or paper mailing list if you’re old-school). Usually you will need to identify avenues of potential publicity in your book proposal itself. This is one of the biggest myths/ misconceptions/ disappointments first-time authors face.
The reality of being an author these days is that you need to be devoting time each and every day to building up your author website and growing your social media/ your mailing list so that when your book comes out, you have enough of your own people buying it to create some momentum. This is the only guaranteed way to make sure your book gets rolling in Amazon and the other major booksellers, and it is certainly the only way a major publisher is going to ask you back again for another book deal.
Of course, once you’ve been through the whole process of getting a book deal, working with an editor, having your book come out, promoting it, then getting your first (very tiny) royalty check, you are probably going to decide that self-publishing is actually a much better option.
That’s where having built up your audience is going to suddenly be very lucrative. When you control the audience, you don’t need a gatekeeper to give you a book deal. When you control the audience and master the basics of self publishing, you can put anything out, anytime you want.