Sitting still for more than a few minutes wasn't a requirement for most people until very recently... You could just be "energetic" or "absent minded" or whatever. Maybe you often get distracted or are disorganized, that's not a disorder, that's just a disposition

It didn't really become a mental disorder until sitting and paying attention for 6+ hours a day became something everyone must do. And then it wasn't the kids complaining that anyone cared about, they were trying to "fix" disruptive or inattentive kids