Frustration, impatience, propensity for impulsive decision-making, lack of concentration and focus, lack of conviction regarding their method, they don't know what to look for, randomness, a tendency to overcomplicate things.
They try to predict rather than make decisions based on what the market is signalling it will do, they don't know what to look for.
because they're really gamblers not traders, they're not prudent and in it for the long haul, lack of experience.
This specific skill takes years to learn and is one of the most difficult so no surprise people have difficulty.
Furthermore, the market conditions are constantly changing so all the mistakes made and learned in the prior day are not necessarily applicable the following day.