You need to when you're starting out. Like a YouTube channel. I would post in comment sections saying "check my channel out if you like these kinds of videos" or something similar. I try not to spam too much though. You need to start somewhere. Like if you're pitching an idea to producers on a movie you want to make or showing your book to a publisher and try to get it published. If you want your product/channel/movie/book etc. to grow and become more popular then you [i]need[/i] to self advertise.