Stock market is very different from crypto market, and the ones who invest in stock market aren't interested in crypto market. The margin of profit in stock market is quite low against crypto market, but investing in stock market is quite safe when you compare in to crypto market. I would also like to clear the fact that Bitcoin doesn't gives to 20-30% return in one day, and I'm quite sure that no other crypto currency would give you 20% or more a day.

Those people who earn 20% or more from a crypto currency are often the lucky ones because most people would rather lose 20-30%  a week or more if they invest in pretty low quality crypto currency, which is mainly made for pump and dump schemes. Those coins wont give you profits all of the time because they are prone to manipulation, and often whales, and huge exchanges manipulate the price of those coins.

Although, it's possible to earn 100x with some coins in span of a year, but those coins are the lucky gems, and only lucky investors can find those gems that could give them 100x or more in profit per year. If you take the example of Bitcoin then it could give profit of 100 - 200%  per two years. In its current position it would be hard for Bitcoin to pump at 20% per day, however, 5% to 10% can happen few times even with Bitcoin.