The answer to that question that I see is that the government is responsible to step in when someone else get hurt under humanitarian obligations. If you make someone responsible for an outcome then they will likely want to implement rules to reduce their own risks.
The rules should of course be proportional to the risk and balanced. It make sense that drugs and driving should not be combined and which outcome can't be fixed afterward. Parenting and drugs are also a pretty problematic area, but it is difficult for the government to make a law against that combination without banning drugs completely. If people took drugs while working with heavy equipment, makes decisions that impact people, work within health care or education, then there is an additional increased risk that the government is expected to manage.
ADHD medicine, especially the non-self medicated versions, have the opposite effect for the government. It reduces the risk that they have to step. If all the other alternatives have failed and you found a solution that do work then that is good and the law might then need to change to incorporate that success. It doesn't however change the reason why the government might still want to tell you what you can and cannot put into your own body.
Where I live we also have universal health care and meth stresses the heart quite a lot. The result is that when the heart start to fall apart it is the government that has to pay for repairs, and those are often quite expensive surgeries that need to be redone every few years. I am no doctor so I can't answer if 10mg is small enough to be safe, but if I was taking it I would find a doctor and do regular heart checkups.