With porn, I think the privacy people want are provided well enough by credit cards. They just need privacy from their spouses, not from the government.

With gambling, there isn't enough social censure to care about privacy, people just do it in the open. As for regulations, I think crypto was more commonly used for gambling than fiat, prior to gambling of all kinds becoming more legalized in the US.

(Which raises another question: if it's skirting regulations that people care about most, why does the hard money feature of bitcoin matter that much? Bitcoin seems to be solving for an additional problem that the gamblers may not care about)

With drugs, I wouldn't know since I just don't know much about the structure of that market. But bitcoin doesn't seem ideal, since its privacy characteristics are not great; and lightning may be too much work for someone who just want to get high, or an addict?

I remember reading a (very old) academic article which argued that evidence is consistent with bitcoin being used for cross-border payments. I, too, think that one of bitcoin's most promising use-cases is international payments and remittances. Would love it if someone on SN could point us to a more up-to-date study on that area of adoption (if any, and if not, perhaps someone could do the research themselves)