People should know that they amount of money you invest on Bitcoin will determine how the profit will turn out. Anyone who believes that buying $20 worth of Bitcoin monthly will make them get rich quick is deceiving themselves. With the worth of Bitcoin, buying such an amount monthly will take a long time to bring high returns. Anyway, it is better to buy with the amount you have than not investing at all. So people with such amount can still buy but they shouldn't expect to become rich overnight.
But you still see people advising what I just mentioned, that you can buy as little Bitcoin as you want, which is true, but some still believe in the misconception that it'll yield them a decent profit. Whether some people like it or not, using $20 per month to buy Bitcoin isn't enough, at this point, you shouldn't focus on using the $20 for Bitcoin, but on how to increase your income and how to budget your funds better.
Usually such type of "investors" quickly give up, seeing that their mere investment hasn't flourished, or has stayed the same or even lost value, but this advice often circulates the forum.