OP has $20 to invest, does anyone think they should invest it in BTC? If BTC were worth $1 million in x years, he would have $200 minus taxes + inflation and what's the point of all that? That's simply not money that can be used to do anything serious except maybe buy a lottery ticket and hope for a miracle.
Yeah but at the same time, people should start somewhere. You put in 20 dollars now, and then 20 dollars in two weeks, and then a 40 dollars a month later, then 10 dollars a week after that, etc etc. You make moves like that and suddenly at the end of the year you have 300 dollars invested.
You keep doing that, for 20 years, and suddenly, your returns do not look that horrible. Also, remember, some money is better than no money, I would rather him put that into bitcoin, than him putting it in anything else, because he may have zero. It's better to put 20 dollars into bitcoin today, than go buy some apple juice or whatever, instead of that, drink water, save money, and put it in bitcoin. That would make you a lot more money.