People can playing gambling secretly without anyone know including their companion or their family. That will not be a problem if they can control themselves from the temptation because I know some friends also playing gambling secretly but they can strictly to themselves.

They know they can addicted to gambling easily so they are take care themselves and careful when gambling. They don't want to have a bad experience from gambling because they already knew many bad examples from their environment. Honestly will be the important thing for a couple and not hiding anything even if that is gambling.