Those folks (myself included) had other careers that they were in but decided they needed a change. You'll see that sometimes in life, what you want when you're 17/18/19 is definitely not: a) what you end up doing for your life and b) not necessarily what is best for you, and you realize it later. It's not like I sat until I was 26 in my parent's basement being unproductive and then magically decided to attend pharmacy school.
This is a fallacious mindset. You don't have to "wait around" until you're 40 to start "a career" and I most certainly was not suggesting you do so. Due to your age, you immediately took my statement to imply that I was telling you to chill for 7 years working at Taco Bell or the bowling alley before even attempting to get goin' with your career. With that said, rushing and being over-zealous about the matter won't help you either. That's why you should relax. You have many, many years ahead of you to work and to punch in, punch out and do the rat race don't worry... you'll get your fill of it soon enough and you won't be so eager. You'll be impatient about when vacation comes or when you get to retire next, hah.
No one's implying that you're trying to argue or outwit anyone, least of all me. I understand that a decade is 10 years' time, but you seem to have this impression that if you're not actively pursuing "a career" that you're wasting time, which is not at all the case. THAT said, again, I don't think anyone here is going to tell you to go sit and smoke pot for 6 years and then get started. Not at all. I just think you need to relax, like I said before.