There are casinos that are truly provably fair, there is no doubt that some of them are not legit even if they claim so but others are so you shouldnt call every casino a scam.
There was one user called something like keepinquiet who exposed 999dice and has recently exposing other casinos that claim to be provably fair and are not, i would not advise anyone to play on those casinos that he exposed.
"Provably fair" is not an empty slogan. If a site is truly provably fair, you would be able to check the bet fairness yourself and you don't need to trust the site blindly. Unless you believe there is a loophole in the hash algorithm, I don't understand why you would think a site could cheat you without you noticing.
P.S: 50 red streak not my bet but i've read in other thread