Even if you have invested in coins during ICO which you think have potential in future, you can't know when it will get listed and you can sell them for profit. But if you invest in this gambling sites you can divest instantly or invest more whenever you want also there is no guarantee that you will make profit on selling those coins on listing. But investing in gambling make you quite sure that actually you will make some if you keep it in bankroll for long time.

Don't just pull out/divest your investment when sites is making loss.