Not to mention countless people that use Caffeine. I know of a number of smart people that use stimulants like Adderall but they probably aren't publicly open about it.
It's not stupid or ridiculous. If a drug benefits a person then what's the problem? Certainly improving focus or intelligence is a much nobler act than people who do drugs for fun. A pervasive and semi-legal part of our culture.
But a culture that's accepting of drug use for enhanced cognition is stupid (reckless is a better word). It'd be no different than performance enhancing drugs in sports. You've got a situation there where people feel uncompetitive without drugs. You don't want that in the workplace.
But it's more than that. The world isn't a zero sum game like sports. One person winning doesn't mean someone else has to lose. I think the world would be much better off if we could increase the IQ and focus of everyone. So much stuff doesn't get done, so many people don't reach their potential, and the whole worlds productivity is much lower than it could be.
If shit drugs like alcohol, which causes tons of deaths, or nicotine, which is incredibly addictive, are legal, then why shouldn't much less dangerous, actually beneficial drugs be legal?
And yeah, it might very well be that ceteris non paribus, but that's case-specific, and doesn't mean that giving people tools and options stops being good.