Why is energy not conserved in Inelastic Collisions?

it is not conserved since in an inelastic collision...for example a marble bouncing on a tiled floor...energy is dissipated and lost at the moment of impact between marble and tile as heat (marginal), sound (obviously since we can hear a sound when the marble hits the floor) and another marginal factor is air resistance while the ball is dropping since air is essentially NOT a frictionless medium.