Hyip sites will scam you means you will be cheated by some one but in gambling you will try your luck with some sort of games, if you lose than you will get some kind on enjoyment or thrill from these games. So I think these two are not same like you said.
Both in HYIP and gambling we need only luck factor to make any money from our investments.
Without luck we cannot expect any returns from both of these programs. I believe there is no control over our money in both gambling and HYIP programs. So, only luck is needed to secure any returns from it.
Yes gambling need luck factor to win but for HYIP I dont think so because that is not the same thing as gambling because with gambling you earn your money by yourself but HYIP you are making investment, but that is a scam investment there so there is no way you can use luck factor on hyip. From the start you invest there you will already lose it but with gambling you will still have a chance to get some profit too so both of these have too much difference