I have things that I can confidently call conworlds going back to my middle school days in the late 90s.
My current Lonely Galaxy setting is a rework of an earlier project I called variously The Last Grand Adventure or En after the in-universe name of the world. It has roots going back to my freshman year of college in the early 2000s.
I conworld mainly as a means of escapism. My current conworld was born out of a time of extreme stress. I couldn’t handle the real world, so I retreated into my own. Perhaps not the most healthy way to cope, but eh.
As long as I can remember, I’ve been interested in fantasy. Later dignified by Tolkien’s quote about escapism - I am like you a partisan for that internal liberty, to imagine vividly, and find solace and meaning in myth making.
I like to think that as we gnaw on these imaginary bones, we are at least sharpening our teeth.