I personally hate the phrase "only invest what you can afford to lose", because those that need to invest the most can't really "afford" to lose any of it. Every loss hits them hard.

I think talking about it as discretionary income, or investing what you might spend on entertainment or things that aren't necessities is better. Of course, that may be a slightly longer conversation, and to many it may be the same thing, but it's worth the effort.

Many have not gotten into crypto, and didn't years ago, because they didn't feel like they could afford to lose even a few bucks.

I think it's worth investing even a few bucks though, even if there isn't as much stress or annoyance. Especially when starting out. You need to get a feel for the markets and get used to the ups and downs. Even after years that can be hard. It will be tremendously hard if someone's first investment is $1000 and the idiot buys Bitcoin at the peak. They might just sell it right away and then find out a few years later that after their lose of a ton of money, it actually doubled from where it was.