One of the common reason is that they aren't really that patient enough to wait up for profits knowing that investing on gambling bankroll isn't really that big for a return
unlike if you do just simply put a bet on a gambling site then you would possibly earn 2x of your money in a matter of seconds.So majority do choose this path instead on
considering making investment and you are right where people do have different choices since we do have different insights in life and ways on how to manage our money.
It's not only about patience.
I've invested in the bankroll long ago. I don't even remember which casino was it.
The casino was young, the total bankroll was probably small (bitcoin price was small too). My investment was also rather small.
However, when I've checked some weeks later, I was losing money. Maybe it was a mistake, maybe it was my lack of knowledge and patience, I withdrew my remaining money to contain the damage. I've never invested in bankroll again.
So it's a risky investment, which requires some knowledge, patience and money you afford to lose.
PS. Please don't compare investing with gambling. Gambling is not a way to earn money (because a good win vs lose ratio is obviously not guaranteed).