This bitcoin is a risk, risk will pay you money or make you lose money, but it is a risk. Not a job, a job will pay you for x amount of work. In a way you can expect to get paid for x amount of work in a pool, but you still are taking a risk. Sorry if you can't see it that way. But that is what it is. If you have invested large sums of money to mine bitcoin, there is no guarantee you will receive what reward you expect, there is no guarantee here. I don't care, or rather it don't care how much math you throw at it.
If I take risk to mean the possibility of things happening that are outside of one's control, everything involves risk (e.g., my boss may default on a loan to the business and I'll find the doors locked and the pay I've earned gone when I show up in the morning).
Gain (or loss) on some risk-taking endeavor is always affected by those who make better (or worse) guesses than I, have better (or worse) timing than I, or do a better (or worse) job of scamming. Still, I go to work in the mornings, I invest in the stock markets, I mine bitcoins, and I hope for more than enough profit in the long run to offset my losses.