Hacker News is generally lucky to be a community of extremely well-organized and put-together people, often with a bit of social clout and wealth. I've noticed on many threads an obliviousness to the fact you've pointed out.
Even In the USA or EU, a significant proportion of people do not have access to something like buying some Apple stock legitimately. Just think of all the people who use those extortionate "cash apps" and payday loan services. Why not just use a bank? The same reason they're not going to be buying Apple stock the proper way.
Most obviously, perhaps no bank account, or no ID. They may not have legal status in the country they live in. They may owe child support. Or tens of thousands of unpaid fines for criminal convictions. Or they have a garnishment against them. Or banks simply won't open an account for them because of bad credit. So on and so on, reasons legitimate, and not, for not engaging with the formal financial system.
This adds up to something like 5 - 20% of Americans depending how you set your threshold. To those people, both cryptocurrencies and possibly-scam crypto-investments are attractive because they offer something otherwise not available.