I understand why you say that. Mining is really much more profitable than investing in ICO. But in terms of start-up capital, it is much more expensive.
This is what stops many from trying to mine coins, to become a trader you do not really need a big capital, there were many stories in the past of traders that started with less than a thousand dollars and now are rich.
But with mining you will need a lot of money and you still need to select the right coin to mine, you could take your chances with new coins and expect that at some point in the future those coins become valuable but that is a very risky bet not much different than investing in icos.