See, I am the complete opposite. I do not care much for downers ( besides weed which to me is not that much of a downer). I much prefer the uppers. Have never done meth and doubt I ever would but I do amphetamines ( speed ) which is my downfall. Yes, it will keep you up at all day and night, does give circles around the eyes ( due to lack of sleep obviously ) but you just don't care because the high in the beginning is so darn phenomenal. Would I not take them if I could go back in time. Yes, most definitely. I would stay away from it and never look back. Well, I have no time machine so I am now sort of hooked. I wanted to say that the people you speak of probably don't care what the drug is doing to them since it is such an addictive drug. When the high goes away, a part of them cares I am sure. The need for it though sort of silences that voice inside.
Peace.