Going through your life well into adulthood while being told "Oh, that's normal. Everyone does that." can make it a bit different. People in this situation may also learn to try to compensate for it, but it can sometimes only do so much; until they hit a brick wall and can't further progress with their lives.

The constant questioning to yourself of do you actually have the disorder, maybe you just need even more sleep, or maybe your mind is just making it up can plague adults who've dealt with it unmitigated their whole lives. The feeling does fade, but it can take time.

I imagine the culture which a lot of millennials also grew up in, with D.A.R.E. and the rebounding effect of the war on drugs could also play a subconscious factor of thinking "meth" is bad and only done by meth-heads and crazy people.