Whilst I think Alf understands the complexity behind the human condition better than most; vilas has a simple but correct point - if Speed decays 20-30 knots below Vapp then either the pilots are not scanning/observing the speed or they are and don't comprehend the situation.
One is closer to negligent behaviour and more straightforward and the other is much more complex and involves training, recruitment, fatigue, SOPs, CRM and so on.... So it really then depends on where you place the crew in any incident on that scale and more importantly where their management places them.