Your image doesn’t belong to you. You’re part of the world and anyone who sees you in it has the right to record that image, when you’re not in a place where you’d have a reasonable expectation of privacy.
As a photographer it’s an issue that really annoys me in the other direction - I’ve seen some people doing things that would make amazing shots, and asked them if I could take their picture and been told no (even though I had every legal right to do so). Then there’s the problem that when you ask someone to take their picture they stop doing what they’re doing and pose awkwardly when you really wanted a candid shot. If someone is taking a picture of you singing, it’s because they liked something about the image they were seeing while you were singing. I’m not saying they should never ask permission, or be otherwise respectful, but you need to get over yourself.