I don't know server seed
You're not supposed to know the secret until later. The server seed changes and it is publicly displayed in front of you before you bet. You can also change the client seed, and it allows a large enough number of values that don't compute to any range of numbers you think the site can focus on. And even if it did, you simply bet high instead of low or the other way around.
The secret has been committed since the start of the day.
The server seed has been committed since your last roll. You can see it.
Client seed is something you can change. High or Low roll is something you can pick.
Providing your own randomly generated string guarantees that PD can not be able to precompute an image that results to a loss.
Add those all up and tell me it is not fair? The site does not even care how much your bet is. The roll is determined on the seeds alone.
I also don't know what was the client seed when I played that game and frankly i don't know how to verify them.
And it's their fault you don't know what client seed you used?
Provably Fair Gaming means you can verify each bet to ensure you always get a fair deal. Modern cryptographic algorithms such as the SHA512 hash algorithm computes the fair random number.
What you think and believe in, may not coincide with the mathematical certainty right in front of your eyes, but if a 1 in 2^512 odds of the calculation being computed wrong or having an intentional collision isn't good enough for you, I don't know what is.
I've played enough of all the dice sites combined to personally see 7 losses in a row on 90%.