Take the NZT himself? He had access to the manufacturer of the pills as evidenced by the last interaction with Eddie.
shareHe explained it himself - the skills he had were "earned" through experience, hard work and selling out by marrying the boss's daughter.
Someone like Carl would view NZT as a cheat, a shortcut. That's especially be true after seeing people die from it.
There'd have been no point. Carl was already rich as hell. Eddie took NZT out of desperation, he was at rock bottom.
shareCarl didn't own the drug company until later. He told Eddie if he hadn't busy enjoying his new wealth and celebrity hood he could also have bought into the company while the stock was at 33.
He also saw the consequences of taking the drug and Eddie also figured out that Carl had a bad heart for his age and couldn't take increased stress.
I don't know everything. Neither does anyone else