I only realised that I barely had any ability to visualise in the last few years and I'm over 40, it's something that's never been there and because it's not the same as lacking either visual memory or imagination there's not really much in the way of cues to make it obvious - the last time I was asked to "picture this in your head" was probably at school three decades ago...

Given I can replay music in my head on demand (called audiation according to a comment below!) with reasonable fidelity even for songs I don't have strong memories of, it seems likely my aphantasia is the developmental deficit of the connection between visual memory and my executive function due to ADHD in both stability and throughput.