A huge multitude of reasons.
They might simply be happy with the gains they have made and choose to hang up the............ whatever.
They have a change of lifestyle or simply drift away from the forums.
Really I mainly come here to learn more about and perfect the practice of Penis Enlargement. But since the vets have already learned all they need to about making gains, they may no longer have a reason. The possibilities are endless. Some simply choose to stop posting