It's fun to speculate on why that's the case, but it seems likely intractable to nail down.

Although, I'll point out that while they're both categories of addiction, pension funds can only invest in and make profits from the more "innocent-feeling" category.

I'd guess that, if there were a regulatory environment that allowed for public companies that could legally encourage people to indulge their $taboo_addiction, then said $taboo_addiction would cease to be taboo and become more prevalent, for better and worse.