In HYIP, the owner can close it and take away all the money as and when he wishes so there is a high risk of losing your capital. At least in gambling, your chance of winning is slightly lesser than the house. Many gambling sites are provably fair where you can verify your roll after your bet.
Yes, but many treat predicting moment of owner exit as gamble. They suspect that will happen eventually and try back out before that happen.
And there were many cases of scammy gambling houses cheating on people or doing 'exit scams' too. It was not that rare sight some years ago.