What I'm attempting (and maybe failing) to say is that it's a key part of how you perceive the world. To you it isn't really a big deal, but people who do think this way just view their own thoughts in a fundamentally different fashion, and the idea of such a big difference in that regard is kind of scary or upsetting to think about for some people. I personally think I would be very sad if I suddenly developed aphantasia, even though I don't think my imagination is as vivid as others.